The Oracle database initialization parameters in the init.ora file are distinct from gateway initialization parameters. Set the gateway parameters in the initialization parameter file using an agent-specific mechanism, or set them in the Oracle data dictionary using the DBMS_HS package. The gateway initialization parameter file must be available when the gateway is started.
This appendix contains a list of the gateway initialization parameters that can be set for each gateway and their description. It also describes the initialization parameter file syntax. It includes the following sections:
The syntax for the initialization parameter file is as follows:
The file is a sequence of commands.
Each command should start on a separate line.
End of line is considered a command terminator (unless escaped with a backslash).
If there is a syntax error in an initialization parameter file, none of the settings take effect.
Set the parameter values as follows:
[SET][PRIVATE] parameter=value
Where:
parameter is an initialization parameter name. It is a string of characters starting with a letter and consisting of letters, digits and underscores. Initialization parameter names are case sensitive.
value is the initialization parameter value. It is case sensitive. An initialization parameter value is either:
A string of characters that does not contain any backslashes, white space or double quotation marks (")
A quoted string beginning with a double quotation mark and ending with a double quotation mark. The following can be used inside a quoted string:
backslash (\) is the escape character
\n inserts a new line
\t inserts a tab
\" inserts a double quotation mark
\\ inserts a backslash
A backslash at the end of the line continues the string on the next line. If a backslash precedes any other character then the backslash is ignored.
For example, to enable tracing for an agent, set the HS_FDS_TRACE_LEVEL initialization parameter as follows:
HS_FDS_TRACE_LEVEL=ON
SET and PRIVATE are optional keywords. You cannot use either as an initialization parameter name. Most parameters are needed only as initialization parameters, so you usually do not need to use the SET or PRIVATE keywords. If you do not specify either SET or PRIVATE, the parameter is used only as an initialization parameter for the agent.
SET specifies that, in addition to being used as an initialization parameter, the parameter value is set as an environment variable for the agent process. Use SET for parameter values that the drivers or non-Oracle system need as environment variables.
PRIVATE specifies that the initialization parameter should be private to the agent and should not be uploaded to the Oracle database. Most initialization parameters should not be private. If, however, you are storing sensitive information like a password in the initialization parameter file, then you may not want it uploaded to the server because the initialization parameters and values are not encrypted when uploaded. Making the initialization parameters private prevents the upload from happening and they do not appear in dynamic performance views. Use PRIVATE for the initialization parameters only if the parameter value includes sensitive information such as a user name or password.
SET PRIVATE specifies that the parameter value is set as an environment variable for the agent process and is also private (not transferred to the Oracle database, not appearing in dynamic performance views or graphical user interfaces).
This section lists all the initialization file parameters that can be set for the Oracle Database Gateway for Teradata. They are as follows:
The following sections describe all the initialization file parameters that can be set for gateways.
| Property | Description |
|---|---|
| Default value | WORLD |
| Range of values | 1 to 199 characters |
Specifies a unique network sub-address for a non-Oracle system. The HS_DB_DOMAIN initialization parameter is similar to the DB_DOMAIN initialization parameter, described in the Oracle Database Reference. The HS_DB_DOMAIN initialization parameter is required if you use the Oracle Names server. The HS_DB_NAME and HS_DB_DOMAIN initialization parameters define the global name of the non-Oracle system.
|
Note: TheHS_DB_NAME and HS_DB_DOMAIN initialization parameters must combine to form a unique address in a cooperative server environment. |
| Property | Description |
|---|---|
| Default value | 01010101 |
| Range of values | 1 to 16 hexadecimal characters |
Specifies a unique hexadecimal number identifying the instance to which the Heterogeneous Services agent is connected. This parameter's value is used as part of a transaction ID when global name services are activated. Specifying a nonunique number can cause problems when two-phase commit recovery actions are necessary for a transaction.
| Property | Description |
|---|---|
| Default value | HO |
| Range of values | 1 to 8 characters |
Specifies a unique alphanumeric name for the data store given to the non-Oracle system. This name identifies the non-Oracle system within the cooperative server environment. The HS_DB_NAME and HS_DB_DOMAIN initialization parameters define the global name of the non-Oracle system.
| Property | Description |
|---|---|
| Default value | 100 |
| Range of values | 1 to 4000 |
Specifies the maximum number of entries in the describe cache used by Heterogeneous Services. This limit is known as the describe cache high water mark. The cache contains descriptions of the mapped tables that Heterogeneous Services reuses so that it does not have to re-access the non-Oracle data store.
If you are accessing many mapped tables, increase the high water mark to improve performance. Increasing the high water mark improves performance at the cost of memory usage.
| Property | Description |
|---|---|
| Default value | System-specific |
| Range of values | Any valid language name (up to 255 characters) |
Provides Heterogeneous Services with character set, language, and territory information of the non-Oracle data source. The value must use the following format:
language[_territory.character_set]
|
Note: The globalization support initialization parameters affect error messages, the data for the SQL Service, and parameters in distributed external procedures. |
Ideally, the character sets of the Oracle database and the non-Oracle data source are the same. In almost all cases, HS_LANGUAGE should be set exactly the same as Oracle database character set for optimal character set mapping and performance. If they are not the same, Heterogeneous Services attempts to translate the character set of the non-Oracle data source to the Oracle database character set, and back again. The translation can degrade performance. In some cases, Heterogeneous Services cannot translate a character from one character set to another.
|
Note: The specified character set must be a superset of the operating system character set on the platform where the agent is installed. |
As more Oracle databases and non-Oracle databases use Unicode as database character sets, it is preferable to also run the gateway in Unicode character set. To do so, you must set HS_LANGUAGE=AL32UTF8. However, when the gateway runs on Windows, the Microsoft ODBC Driver Manager interface can exchange data only in the double-byte character set, UCS2. This results in extra ratio expansion of described buffer and column sizes. Refer to HS_FDS_REMOTE_DB_CHARSET for instruction on how to adjust to correct sizes.
The language component of the HS_LANGUAGE initialization parameter determines:
Day and month names of dates
AD, BC, PM, and AM symbols for date and time
Default sorting mechanism
Note that Oracle does not determine the language for error messages for the generic Heterogeneous Services messages (ORA-25000 through ORA-28000). These are controlled by the session settings in the Oracle database.
The territory clause specifies the conventions for day and week numbering, default date format, decimal character and group separator, and ISO and local currency symbols. Note that the level of globalization support between the Oracle database and the non-Oracle data source depends on how the gateway is implemented.
| Property | Description |
|---|---|
| Default value | 64 KB |
| Range of values | Any value up to 2 GB |
Sets the size of the piece of LONG data being transferred. A smaller piece size means less memory requirement, but more round-trips to fetch all the data. A larger piece size means fewer round-trips, but more of a memory requirement to store the intermediate pieces internally. Thus, the initialization parameter can be used to tune a system for the best performance, with the best trade-off between round-trips and memory requirements, and network latency or response time.
| Property | Description |
|---|---|
| Default value | 50 |
| Range of values | 1 to the value of Oracle's OPEN_CURSORS initialization parameter |
Defines the maximum number of cursors that can be open on one connection to a non-Oracle system instance.
The value never exceeds the number of open cursors in the Oracle database. Therefore, setting the same value as the OPEN_CURSORS initialization parameter in the Oracle database is recommended.
| Property | Description |
|---|---|
| Default value | ON |
| Range of values | OFF or ON |
Controls whether Heterogeneous Services attempts to optimize performance of data transfer between the Oracle database and the Heterogeneous Services agent connected to the non-Oracle data store.
The following values are possible:
OFF disables reblocking of fetched data so that data is immediately sent from agent to server.
ON enables reblocking, which means that data fetched from the non-Oracle system is buffered in the agent and is not sent to the Oracle database until the amount of fetched data is equal or higher than the value of HS_RPC_FETCH_SIZE initialization parameter. However, any buffered data is returned immediately when a fetch indicates that no more data exists or when the non-Oracle system reports an error.
| Property | Description |
|---|---|
| Default value | 50000 |
| Range of values | 1 to 10000000 |
Tunes internal data buffering to optimize the data transfer rate between the server and the agent process.
Increasing the value can reduce the number of network round-trips needed to transfer a given amount of data, but also tends to increase data bandwidth and to reduce latency as measured between issuing a query and completion of all fetches for the query. Nevertheless, increasing the fetch size can increase latency for the initial fetch results of a query, because the first fetch results are not transmitted until additional data is available.
| Property | Description |
|---|---|
| Default value for '[+|-]hh:mm' | Derived from the NLS_TERRITORY initialization parameter |
| Range of values for '[+|-]hh:mm' | Any valid datetime format mask |
Specifies the default local time zone displacement for the current SQL session. The format mask, [+|-]hh:mm, is specified to indicate the hours and minutes before or after UTC (Coordinated Universal Time—formerly Greenwich Mean Time). For example:
HS_TIME_ZONE = [+ | -] hh:mm
| Property | Description |
|---|---|
| Default Value | COMMIT_CONFIRM |
| Range of Values | COMMIT_CONFIRM, READ_ONLY, SINGLE_SITE, READ_ONLY_AUTOCOMMIT, SINGLE_SITE_AUTOCOMMIT |
Specifies the type of transaction model that is used when the non-Oracle database is updated by a transaction.
The following values are possible:
COMMIT_CONFIRM provides read and write access to the non-Oracle database and allows the gateway to be part of a distributed update. To use the commit-confirm model, the following items must be created in the non-Oracle database:
Transaction log table. The default table name is HS_TRANSACTION_LOG. A different name can be set using the HS_FDS_TRANSACTION_LOG parameter. The transaction log table must be granted SELECT, DELETE, and INSERT privileges set to public.
Recovery account. The account name is assigned with the HS_FDS_RECOVERY_ACCOUNT parameter.
Recovery account password. The password is assigned with the HS_FDS_RECOVERY_PWD parameter.
READ_ONLY provides read access to the non-Oracle database.
SINGLE_SITE provides read and write access to the non-Oracle database. However, the gateway cannot participate in distributed updates.
READ_ONLY_AUTOCOMMIT provides read only access to the non-Oracle database that does not use logging.
SINGLE_SITE_AUTOCOMMIT provides read and write access to the non-Oracle database without logging. The gateway cannot participate in distributed updates. Moreover, any update to the non-Oracle database is committed immediately.
| Property | Description |
|---|---|
| Default value | None |
| Range of values | Valid parameter file names |
Use the IFILE initialization parameter to embed another initialization file within the current initialization file. The value should be an absolute path and should not contain environment variables. The three levels of nesting limit do not apply.
| Property | Description |
|---|---|
| Default Value | None |
| Range of Values | Not applicable |
HS_FDS_CONNECT_INFO that describes the connection to the non-Oracle system.
The default initialization parameter file already has an entry for this parameter. The syntax for HS_FDS_CONNECT_INFO for the gateway is as follows:
HS_FDS_CONNECT_INFO=host_alias:port_number[/database_name]
where, host_alias is the host alias name or IP address of the machine hosting the Teradata database, port_number is the port number of the Teradata database server, and database_name is the Teradata database name. The database_name variable is optional.
This release supports IPv6 format, so you can enter IPv6 format in place of hostname, but you need to wrap square brackets around the IPv6 specification.
For example,
HS_FDS_CONNECT_INFO=[2001:0db8:20c:f1ff:fec6:38af]:port_number/…
| Property | Description |
|---|---|
| Default Value | None |
| Range of Values | Not applicable |
The name of the table owner that is used for the non-Oracle database tables if an owner is not specified in the SQL statements.
|
Note: If this parameter is not specified and the owner is not explicitly specified in the SQL statement, then the user name of the Oracle user or the user name specified when creating the database link is used. |
| Property | Description |
|---|---|
| Default Value | FALSE |
| Range of Values | TRUE, FALSE |
Enables return values from functions. By default, all stored procedures and functions do not return a return value to the user.
|
Note: If you set this initialization parameter, you must change the syntax of the procedure execute statement for all existing stored procedures to handle return values. |
| Property | Description |
|---|---|
| Default Value | RECOVER |
| Range of values | Any valid user ID |
Specifies the name of the recovery account used for the commit-confirm transaction model. An account with user name and password must be set up at the non-Oracle system. For more information about the commit-confirm model, see the HS_TRANSACTION_MODEL parameter.
The name of the recovery account is case sensitive.
| Property | Description |
|---|---|
| Default Value | RECOVER |
| Range of values | Any valid password |
Specifies the password of the recovery account used for the commit-confirm transaction model set up at the non-Oracle system. For more information about the commit-confirm model, see the HS_TRANSACTION_MODEL parameter.
The name of the password of the recovery account is case sensitive.
| Property | Description |
|---|---|
| Default Value | OFF |
| Range of values | OFF, ON, DEBUG |
Specifies whether error tracing is turned on or off for gateway connectivity.
The following values are valid:
OFF disables the tracing of error messages.
ON enables the tracing of error messages that occur when you encounter problems. The results are written by default to a gateway log file in LOG directory where the gateway is installed.
DEBUG enables the tracing of detailed error messages that can be used for debugging.
| Property | Description |
|---|---|
| Default Value | HS_TRANSACTION_LOG |
| Range of Values | Any valid table name |
Specifies the name of the table created in the non-Oracle system for logging transactions. For more information about the transaction model, see the HS_TRANSACTION_MODEL parameter.
| Property | Description |
|---|---|
| Default Value | 100 |
| Range of Values | Any integer between 1 and 1000 |
| Syntax | HS_FDS_FETCH_ROWS=num |
HS_FDS_FETCH_ROWS specifies the fetch array size. This is the number of rows to be fetched from the non-Oracle database and to return to Oracle database at one time. This parameter will be affected by the HS_RPC_FETCH_SIZE and HS_RPC_FETCH_REBLOCKING parameters.
| Property | Description |
|---|---|
| Default Value | 0 (no timeout) |
| Range of Values | 0-9999 (minutes) |
| Syntax | HS_IDLE_TIMEOUT=num |
This feature is only available for Oracle Net TCP protocol. When there is no activity for a connected gateway session for this specified time period, the gateway session would be terminated automatically with pending update (if any) rolled back.
| Property | Description |
|---|---|
| Default Value | BYTE |
| Range of Values | BYTE | CHAR |
| Syntax | HS_NLS_LENGTH_SEMANTICS = { BYTE | CHAR } |
This release of gateway has Character Semantics functionality equivalent to the Oracle Database Character Semantics, that is, NLS_LENGTH_SEMANTICS. When HS_NLS_LENGTH_SEMANTICS is set to CHAR, the (VAR)CHAR columns of Teradata are to be interpreted as having CHAR semantics. The only situation the gateway does not honor the HS_NLS_LENGTH_SEMANTICS=CHAR setting is when both Oracle database and the gateway are on the same multi-byte character set
| Property | Description |
|---|---|
| Default Value | OFF |
| Range of Values | OFF | LOCAL | REMOTE |ALL |
| Syntax | HS_KEEP_REMOTE_COLUMN_SIZE = OFF | LOCAL | REMOTE | ALL |
| Parameter type | String |
HS_KEEP_REMOTE_COLUMN_SIZE specifies whether to suppress ratio expansion when computing the length of (VAR)CHAR datatypes during data conversion from non-Oracle database to the gateway, and then to the Oracle database. When it is set to REMOTE, the expansion is suppressed between the non-Oracle database and the gateway. When it is set to LOCAL, the expansion is suppressed between the gateway and the Oracle database. When it is set to ALL, the expansion is suppressed from the non-Oracle database to the Oracle database.
When the parameter is set, the expansion is suppressed when reporting the remote column size, calculating the implicit resulting buffer size, and instantiating in the local Oracle database. This has effect only for remote column size from non-Oracle database to the Oracle database. If the gateway runs on Windows and HS_LANGUAGE=AL32UTF8, then you must not specify this parameter, as it would influence other ratio related parameter operation. It has no effect for calculating ratio for data moving from Oracle database to non-Oracle database through gateway during INSERT, UPDATE, or DELETE.
| Property | Description |
|---|---|
| Default Value | None |
| Range of values | Not applicable |
| Syntax | HS_FDS_REMOTE_DB_CHARSET |
This parameter is valid only when HS_LANGUAGE is set to AL32UTF8 and the gateway runs on Windows. As more Oracle databases and non-Oracle databases use Unicode as database character sets, it is preferable to also run the gateway in Unicode character set. To do so, you must set HS_LANGUAGE=AL32UTF8. However, when the gateway runs on Windows, the Microsoft ODBC Driver Manager interface can exchange data only in the double-byte character set, UCS2. This results in extra ratio expansion of described buffer and column sizes. To compensate, the gateway can re-adjust the column size if HS_FDS_REMOTE_DB_CHARSET is set to the corresponding non-Oracle database character set. For example, HS_FDS_REMOTE_DB_CHARSET=KO16KSC5601.
| Property | Description |
|---|---|
| Default Value | TRUE |
| Range of values | {TRUE|FALSE} |
| Syntax | HS_FDS_SUPPORT_STATISTICS= {TRUE|FALSE} |
We gather statistics from the non-Oracle database by default. You can choose to disable the gathering of remote database statistics by setting the HS_FDS_SUPPORT_STATISTICS parameter to FALSE.
| Property | Description |
|---|---|
| Default Value | 64 |
| Range of values | {64|32} |
| Syntax | HS_FDS_SQLLEN_INTERPRETATION= {64|32} |
This parameter is only valid for 64 bit platforms. ODBC standard specifies SQLLEN (of internal ODBC construct) being 64 bit on 64 bit platforms, but some ODBC driver managers and drivers violate this convention, and implement it as 32 bit. In order for the gateway to compensate their behavior, you need to specify HS_FDS_SQLLEN_INTERPRETATION=32 if you use these types of driver managers and driver.
User's Guide
11g Release 2 (11.2)
E12068-03
January 2012
Oracle Database Gateway for Teradata User's Guide, 11g Release 2 (11.2)
E12068-03
Copyright © 2002, 2012, Oracle and/or its affiliates. All rights reserved.
Primary Author: Maitreyee Chaliha
Contributor: Vira Goorah, Juan Pablo Ahues-Vasquez, Peter Castro, Charles Benet, Peter Wong, and Govind Lakkoju
This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.
The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.
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This chapter introduces the challenge faced by organizations when running several different database systems. It briefly covers Heterogeneous Services, the technology that the Oracle Database Gateway for Teradata is based on.
To get a good understanding of generic gateway technology, Heterogeneous Services, and how Oracle Database Gateways fit in the picture, reading the Oracle Database Heterogeneous Connectivity User's Guide first is highly recommended.
This chapter contains the following sections:
Heterogeneous data access is a problem that affects a lot of companies. A lot of companies run several different database systems. Each of these systems stores data and has a set of applications that run against it. Consolidation of this data in one database system is often hard - in large part because many of the applications that run against one database may not have an equivalent that runs against another. Until such time as migration to one consolidated database system is made feasible, it is necessary for the various heterogeneous database systems to interoperate.
Oracle Database Gateways provide the ability to transparently access data residing in a non-Oracle system from an Oracle environment. This transparency eliminates the need for application developers to customize their applications to access data from different non-Oracle systems, thus decreasing development efforts and increasing the mobility of the application. Applications can be developed using a consistent Oracle interface for both Oracle and Teradata.
Gateway technology is composed of two parts: a component that has the generic technology to connect to a non-Oracle system, which is common to all the non-Oracle systems, called Heterogeneous Services, and a component that is specific to the non-Oracle system that the gateway connects to. Heterogeneous Services, in conjunction with the Oracle Database Gateway agent, enables transparent access to non-Oracle systems from an Oracle environment.
Heterogeneous Services provides the generic technology for connecting to non-Oracle systems. As an integrated component of the database, Heterogeneous Services can exploit features of the database, such as the powerful SQL parsing and distributed optimization capabilities.
Heterogeneous Services extend the Oracle SQL engine to recognize the SQL and procedural capabilities of the remote non-Oracle system and the mappings required to obtain necessary data dictionary information. Heterogeneous Services provides two types of translations: the ability to translate Oracle SQL into the proper dialect of the non-Oracle system as well as data dictionary translations that displays the metadata of the non-Oracle system in the local format. For situations where no translations are available, native SQL can be issued to the non-Oracle system using the pass-through feature of Heterogeneous Services.
Heterogeneous Services also maintains the transaction coordination between Oracle and the remote non-Oracle system, such as providing the two-phase commit protocol to ensure distributed transaction integrity, even for non-Oracle systems that do not natively support two-phase commit.
|
See Also: Oracle Database Heterogeneous Connectivity User's Guide for more information about Heterogeneous Services. |
The capabilities, SQL mappings, data type conversions, and interface to the remote non-Oracle system are contained in the gateway. The gateway interacts with Heterogeneous Services to provide the transparent connectivity between Oracle and non-Oracle systems.
The gateway must be installed on a machine running either the Teradata database or the Teradata client. This machine can be the same machine as the Oracle database or on the same machine as the Teradata database or on a third machine as a standalone. Each configuration has its advantages and disadvantages. The issues to consider when determining where to install the gateway are network traffic, operating system platform availability, hardware resources and storage.
This appendix contains the following sections:
With a few exceptions, the gateway provides full support for Oracle DELETE, INSERT, SELECT, and UPDATE statements.
The gateway does not support Oracle data definition language (DDL) statements. No form of the Oracle ALTER, CREATE, DROP, GRANT, or TRUNCATE statements can be used. Instead, use the pass-through feature of the gateway if you need to use DDL statements against the Teradata database.
|
See Also: Oracle Database SQL Language Reference for detailed descriptions of keywords, parameters, and options. |
The DELETE statement is fully supported. However, only Oracle functions supported by Teradata can be used.
The INSERT statement is fully supported. However, only Oracle functions supported by Teradata can be used.
The SELECT statement is fully supported, with these exceptions:
CONNECT BY condition
NOWAIT
START WITH condition
WHERE CURRENT OF
All functions are evaluated by the Teradata database after the gateway has converted them to Teradata SQL.
Oracle SQL functions with no equivalent function in Teradata are not supported in DELETE, INSERT, or UPDATE statements, but are evaluated by the Oracle database if the statement is a SELECT statement. That is, the Oracle database performs post-processing of SELECT statements sent to the gateway.
If an unsupported function is used in a DELETE, INSERT, or UPDATE, statement, the following Oracle error occurs:
ORA-02070: database db_link_name does not support function in this context
The gateway translates the following Oracle database functions in SQL statements to their equivalent Teradata functions:
| Oracle | Teradata |
|---|---|
= | = |
> | > |
< | < |
>= | >= |
<= | <= |
<>, !=, ^= | <>, != |
IS NOT NULL | IS NOT NULL |
IS NULL | IS NULL |
| Oracle | Teradata |
|---|---|
ABS | ABS |
EXP | EXP |
LOG(a, b) | LOG10(b) / LOG10(a) |
POWER | ** |
SQRT | SQRT |
This manual describes the Oracle Database Gateway for Teradata, which enables Oracle client applications to access Teradata data through Structured Query Language (SQL). The gateway, with the Oracle database, creates the appearance that all data resides on a local Oracle database, even though the data can be widely distributed.
This preface covers the following topics:
This manual is intended for Oracle database administrators who perform the following tasks:
Installing and configuring the Oracle Database Gateway for Teradata
Diagnosing gateway errors
Using the gateway to access Teradata data
|
Note: You should understand the fundamentals of Oracle Database Gateways and the UNIX based platforms before using this guide to install or administer the gateway. |
For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.
Access to Oracle Support
Oracle customers have access to electronic support through My Oracle Support. For information, visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=info or visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=trs if you are hearing impaired.
For more information, see these Oracle resources:
The following text conventions are used in this document:
| Convention | Meaning |
|---|---|
| boldface | Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary. |
| italic | Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values. |
monospace | Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter. |
This appendix contains the following section:
The gateway converts Teradata data types to Oracle data types as follows:
Table A-1 Data Type Conversions
| Teradata | Oracle | Comment |
|---|---|---|
|
|
| |
|
- | ||
|
|
| |
|
|
- | |
|
|
|
- |
|
|
| |
|
|
- | |
|
|
- | |
|
|
with precision <= single precision float | |
|
|
with precision > single precision float | |
|
|
| |
|
|
|
- |
|
if Oracle DB Character Set = Unicode. Otherwise, it is not supported. | ||
|
if Oracle DB Character Set = Unicode. Otherwise, it is not supported | ||
|
|
| |
|
|
- | |
|
|
- | |
|
|
with less or equal to | |
|
|
with more than | |
|
If the size is greater than | ||
|
If the size is 2000 or less, otherwise it is mapped to |
Copyright © 1994-2012, Oracle and/or its affiliates. All rights reserved.
Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.
Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. AMD, Opteron, the AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro Devices. UNIX is a registered trademark of The Open Group.
This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.
The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.
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The Oracle Database Gateway for Teradata User's Guide translates a query that refers to an Oracle database data dictionary table into a query that retrieves the data from Teradata system catalog tables. You perform queries on data dictionary tables over the database link in the same way you query data dictionary tables in the Oracle database. The gateway data dictionary is similar to the Oracle database data dictionary in appearance and use.
This appendix contains the following sections:
The following paragraphs describe the Oracle Database Gateway for Teradata data dictionary support.
Teradata data dictionary information is stored in the Teradata database as Teradata system catalog tables. The Teradata system catalog tables define the structure of a database. When you change data definitions, Teradata reads and modifies the Teradata system catalog tables to add information about the user tables.
Accessing a gateway data dictionary table or view is identical to accessing a data dictionary in an Oracle database. You issue a SQL SELECT statement specifying a database link. The Oracle database data dictionary view and column names are used to access the gateway data dictionary in an Oracle database. Synonyms of supported views are also acceptable. For example, the following statement queries the data dictionary table ALL_CATALOG to retrieve all table names in the Teradata database:
SQL> SELECT * FROM ALL_CATALOG@TERA;
When a data dictionary access query is issued, the gateway:
Maps the requested table, view, or synonym to one or more Teradata system table names. The gateway translates all data dictionary column names to their corresponding Teradata database column names within the query. Refer to "Data Dictionary Mapping" for details.
Sends the translated query to Teradata.
Might convert the retrieved Teradata data to give it the appearance of the Oracle database data dictionary table.
Passes the data dictionary information from the translated Teradata system catalog table to the Oracle database.
|
Note: The values returned when querying the gateway data dictionary might not be the same as the ones returned by the Oracle Enterprise ManagerDESCRIBE command. |
Queries issued directly to individual Teradata system catalog tables are allowed but they return different results because the Teradata system catalog table column names differ from those of the data dictionary view. Also, certain columns in a Teradata system catalog table cannot be used in data dictionary processing.
The gateway supports the following views and tables:
| Supported Views and Tables | Supported Views and Tables |
|---|---|
ALL_CATALOG | ALL_COL_COMMENTS |
ALL_CONS_COLUMNS | ALL_CONSTRAINTS |
ALL_IND_COLUMNS | ALL_INDEXES |
ALL_OBJECTS | ALL_TAB_COLUMNS |
ALL_TAB_COMMENTS | ALL_TABLES |
ALL_USERS | ALL_VIEWS |
DBA_CATALOG | DBA_COL_COMMENTS |
DBA_OBJECTS | DBA_TABLES |
DBA_TAB_COLUMNS | DBA_TAB_COMMENTS |
DICT_COLUMNS | DICTIONARY |
DUAL | USER_COL_COMMENTS |
USER_CATALOG | USER_CONSTRAINTS |
USER_CONS_COLUMNS | USER_INDEXES |
USER_IND_COLUMNS | USER_TAB_COLUMNS |
USER_OBJECTS | USER_TABLES |
USER_TAB_COMMENTS | USER_VIEWS |
USER_USERS |
No other Oracle database data dictionary tables or views are supported. If you use a view not on the list, you receive the Oracle database error code for no more rows available.
Queries through the gateway of any data dictionary table or view beginning with ALL_ can returns rows from the Teradata database even when access privileges for those Teradata objects have not been granted. When querying an Oracle database with the Oracle data dictionary, rows are returned only for those objects you are permitted to access.
The tables in this section list Oracle data dictionary view names and the equivalent Teradata system tables used. A plus sign (+) indicates that a join operation is involved.
Table C-1 Oracle Data Dictionary View Names and Teradata Equivalents
| View Name | Teradata System Table Name |
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There is a minor difference between the gateway data dictionary and a typical Oracle database data dictionary. The Oracle database columns that are missing in a Teradata system catalog table are filled with zeros, spaces, null values, not-applicable values (N.A.), or default values, depending on the column type.
The gateway data dictionary tables and views provide the following information:
Name, data type, and width of each column
The contents of columns with fixed values
They are described here with information retrieved by an SQL*PLUS DESCRIBE command. The values in the Null? column might differ from the Oracle database data dictionary tables and views. Any hardcoded default value is shown to the right of an item, but this is not information returned by DESCRIBE.
Table C-2 ALL_CATALOG
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Table C-3 ALL_COL_COMMENTS
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Table C-4 ALL_CONS_COLUMNS
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Table C-5 ALL_CONSTRAINTS
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Table C-6 ALL_IND_COLUMNS
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Table C-7 ALL_INDEXES
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Table C-8 ALL_OBJECTS
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Table C-9 ALL_TAB_COLUMNS
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Table C-10 ALL_TAB_COMMENTS
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Table C-11 ALL_TABLES
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Table C-13 ALL_VIEWS
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Table C-14 DBA_CATALOG
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Table C-15 DBA_COL_COMMENTS
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Table C-16 DBA_OBJECTS
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Table C-17 DBA_TAB_COLUMNS
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Table C-18 DBA_TAB_COMMENTS
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Table C-19 DBA_TABLES
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Table C-20 DICT_COLUMNS
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Table C-23 USER_CATALOG
| Name | Type | Value |
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Table C-24 USER_COL_COMMENTS
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Table C-25 USER_CONS_COLUMNS
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Table C-26 USER_CONSTRAINTS
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Table C-27 USER_IND_COLUMNS
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Table C-28 USER_INDEXES
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Table C-29 USER_OBJECTS
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Table C-30 USER_TAB_COLUMNS
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Table C-31 USER_TAB_COMMENTS
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Table C-32 USER_TABLES
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Table C-33 USER_USERS
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Table C-34 USER_VIEWS
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The following case studies for Teradata demonstrate some of the features of the Oracle Database Gateway. You can verify that the gateway is installed and operating correctly by using the demonstration files included on the distribution media.
The demonstration files are automatically copied to disk when the gateway is installed.
This chapter contains the following sections:
The cases illustrate:
A simple query (Case 1)
A more complex query (Case 2)
Joining Teradata tables (Case 3)
Write capabilities (Case 4)
A data dictionary query (Case 5)
The pass-through feature (Case 6)
The distribution media contains the following:
Demonstration files.
One SQL script file that creates the demonstration tables in the Teradata database.
One SQL script file that drops the demonstration tables from the Teradata database.
After a successful gateway installation, use the demonstration files stored in the directory $ORACLE_HOME/dg4tera/demo where $ORACLE_HOME is the directory under which the gateway is installed. The directory contains the following demonstration files:
The case studies assume these requirements have been met:
The gateway demonstration tables are installed in the Teradata database.
The Oracle database has an account named SCOTT with a password of TIGER.
The Oracle database has a database link called GTWLINK (set up as public or private to the user SCOTT) that connects the gateway to a Teradata database as SCOTT with password TIGER2.
For example, you can create the database link as follows:
SQL> CREATE DATABASE LINK GTWLINK CONNECT TO SCOTT 2 IDENTIFIED BY TIGER2 USING 'GTWSID';
Oracle Net Services is configured correctly and running.
The case studies are based on the GTW_EMP, GTW_DEPT, and GTW_SALGRADE tables. If the demonstration tables have not been created in the Teradata database, use the bldtera.sql script to create them.
The script creates the demonstration tables in the Teradata database accordingly:
CREATE TABLE GTW_EMP ( EMPNO SMALLINT NOT NULL ENAME VARCHAR(10), JOB VARCHAR(9), MGR SMALLINT, HIREDATE DATETIME, SAL NUMERIC(7,2), COMM NUMERIC(7,2), DEPTNO SMALLINT) CREATE TABLE GTW_DEPT ( DEPTNO SMALLINT NOT NULL, DNAME VARCHAR(14), LOC VARCHAR(13)) CREATE TABLE GTW_SALGRADE ( GRADE REAL, LOSAL NUMERIC(9,4), HISAL NUMERIC(9,4))
The table definitions are listed here using information retrieved by the SQL*PLUS DESCRIBE command:
GTW_EMP
Name Null? Type ------------------------------- -------- ---- EMPNO NOT NULL NUMBER(5) ENAME VARCHAR2(10) JOB VARCHAR2(9) MGR NUMBER(5) HIREDATE DATE SAL NUMBER(7,2) COMM NUMBER(7,2) DEPTNO NUMBER(5)
GTW_DEPT
Name Null? Type ------------------------------- -------- ---- DEPTNO NOT NULL NUMBER(5) DNAME VARCHAR2(14) LOC VARCHAR2(13)
GTW_SALGRADE
Name Null? Type ------------------------------- -------- ---- GRADE FLOAT(53) LOSAL NUMBER(9,4) HISAL NUMBER(9,4)
The contents of the Teradata tables are:
GTW_EMP
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ----- ----- --- --- -------- --- ---- ------ 7369 SMITH CLERK 7902 17-DEC-80 800 20 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7566 JONES MANAGER 7839 02-APR-81 2975 20 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7788 SCOTT ANALYST 7566 09-DEC-82 3000 20 7839 KING PRESIDENT 17-NOV-81 5000 10 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7876 ADAMS CLERK 7788 12-JAN-83 1100 20 7900 JAMES CLERK 7698 03-DEC-81 950 30 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10
GTW_DEPT
DEPTNO DNAME LOC ----- -------------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON
GTW_SALGRADE
GRADE LOSAL HISAL
------ ------ -----
1 700 1200
2 1201 1400
3 1401 2000
4 2001 3000
5 3001 9999
Case 1 demonstrates the following:
A simple query.
A simple query retrieving full date information.
The first query retrieves all the data from GTW_DEPT and confirms that the gateway is working correctly.
Case 2 demonstrates the following:
The functions SUM(expression) and NVL(expr1, expr2) in the SELECT list.
The GROUP BY and HAVING clauses.
This query retrieves the departments from GTW_EMP whose total monthly expenses are higher than $10,000.
Case 3 demonstrates the following:
Joins between Teradata tables.
Subselects.
The query retrieves information from three Teradata tables and relates the employees to their department name and salary grade, but only for those employees earning more than the average salary.
Case 4 is split into three cases and demonstrates the following:
Case 4a demonstrates bind values and subselect. All employees in department 20 and one employee, WARD, in department 30 are deleted.
Case 4b provides an example of a simple UPDATE statement. In this example, employees are given a $100 a month salary increase.
Case 5 demonstrates data dictionary mapping. It retrieves all the tables and views that exist in the Teradata database that begin with "GTW".
Case 6 demonstrates the gateway pass-through feature that allows an application to send commands or statements to Teradata.
This case demonstrates:
A pass-through UPDATE statement using bind variables.
A pass-through SELECT statement.
Case 6a provides an example of a pass-through UPDATE statement with bind variables. In this example, the salary for EMPNO 7934 is set to 4000.
After the gateway is installed and configured, you can use the gateway to access Teradata data, pass Teradata commands from applications to the Teradata database, perform distributed queries, and copy data.
This chapter contains the following sections:
The gateway can pass Teradata commands or statements from the application directly to the Teradata database using the DBMS_HS_PASSTHROUGH package.
Use the DBMS_HS_PASSTHROUGH package in a PL/SQL block to specify the statement to be passed to the Teradata database, as follows:
DECLARE
num_rows INTEGER;
BEGIN
num_rows := DBMS_HS_PASSTHROUGH.EXECUTE_IMMEDIATE@TERA('command');
END;
/
Where command cannot be one of the following:
BEGIN TRANSACTION
BT
COMMIT
END TRANSACTION
ET
ROLLBACK
The DBMS_HS_PASSTHROUGH package supports passing bind values and executing SELECT statements.
|
See Also: Oracle Database PL/SQL Packages and Types Reference and Chapter 3, Features of Oracle Database Gateways, of Oracle Database Heterogeneous Connectivity User's Guide for more information about theDBMS_HS_PASSTHROUGH package. |
Using the procedural feature, the gateway can execute stored procedures that are defined in the Teradata database. It is not necessary to relink the gateway or define the procedure to the gateway, but the procedure's access privileges must permit access by the gateway.
|
See Also: Oracle Database Heterogeneous Connectivity User's Guide for more information about executing stored procedures. |
Standard PL/SQL statements are used to execute a stored procedure.
The gateway supports stored procedures in three mutually exclusive modes:
Normal mode: Have access to IN/OUT arguments only
Return value mode: Have a return value for all stored procedures
Resultset mode: Out values are available as last result set
By default, all stored procedures and functions do not return a return value to the user. To enable return values, set the HS_FDS_PROC_IS_FUNC parameter in the initialization parameter file.
|
See Also: Appendix D, "Initialization Parameters" for information about both editing the initialization parameter file and theHS_FDS_PROC_IS_FUNC parameter. |
|
Note: If you set theHS_FDS_PROC_IS_FUNC gateway initialization parameter, you must change the syntax of the procedure execute statement for all existing stored procedures. |
In the following example, the employee name JOHN SMYTHE is passed to the Teradata stored procedure REVISE_SALARY. The stored procedure retrieves the salary value from the Teradata database to calculate a new yearly salary for JOHN SMYTHE. The revised salary returned in RESULT is used to update EMP in a table of an Oracle database:
DECLARE INPUT VARCHAR2(15); RESULT NUMBER(8,2); BEGIN INPUT := 'JOHN SMYTHE'; RESULT := REVISE_SALARY@TERA(INPUT); UPDATE EMP SET SAL = RESULT WHERE ENAME =: INPUT; END; /
The procedural feature automatically converts non-Oracle data types to and from PL/SQL data types.
The Oracle Database Gateway for Teradata provides support for stored procedures which return result sets.
By default, all stored procedures and functions do not return a result set to the user. To enable result sets, set the HS_FDS_RESULTSET_SUPPORT parameter in the initialization parameter file.
|
See Also: Appendix D, "Initialization Parameters" for information about both editing the initialization parameter file and theHS_FDS_RESULTSET_SUPPORT parameter. For further information about Oracle support for result sets in non-Oracle databases see Oracle Database Heterogeneous Connectivity User's Guide. |
|
Note: If you set theHS_FDS_RESULTSET_SUPPORT gateway initialization parameter, you must change the syntax of the procedure execute statement for all existing stored procedures or errors will occur. |
When accessing stored procedures with result sets through the Oracle Database Gateway for Teradata, you will be in the sequential mode of Heterogeneous Services.
The Oracle Database Gateway for Teradata returns the following information to Heterogeneous Services during procedure description:
All the input arguments of the remote stored procedure
None of the output arguments
One out argument of type ref cursor (corresponding to the first result set returned by the stored procedure)
Client programs have to use the virtual package function dbms_hs_result_set.get_next_result_set to get the ref cursor for subsequent result sets. The last result set returned is the out argument from the procedure.
The limitations of accessing result sets are the following:
Result sets returned by a remote stored procedure have to be retrieved in the order in which they were placed on the wire
On execution of a stored procedure, all result sets returned by a previously executed stored procedure will be closed (regardless of whether the data has been completely
In the following example, the Teradata stored procedure is executed to fetch the contents of the emp and dept tables from Teradata:
CREATE PROCEDURE refcurproc (@arg1 varchar(255), @arg2 varchar(255) output) AS SECLECT @arg2 = @arg1 SELECT * FROM EMP SELECT * FROM DEPT GO
This stored procedure assigns the input parameter arg1 to the output parameter arg2, opens the query SELECT * FROM EMP in ref cursor rc1, and opens the query SELECT * FROM DEPT in ref cursor rc2.
|
Note: Chained mode must be set before creating the stored procedure. Issue the following command in Teradata:set chained on |
The following example shows OCI program fetching from result sets in sequential mode:
OCIEnv *ENVH;
OCISvcCtx *SVCH;
OCIStmt *STMH;
OCIError *ERRH;
OCIBind *BNDH[3];
OraText arg1[20];
OraText arg2[255];
OCIResult *rset;
OCIStmt *rstmt;
ub2 rcode[3];
ub2 rlens[3];
sb2 inds[3];
OraText *stmt = (OraText *) "begin refcurproc@TERA(:1,:2,:3); end;";
OraText *n_rs_stm = (OraText *)
"begin :ret := DBMS_HS_RESULT_SET.GET_NEXT_RESULT_SET@TERA; end;";
/* Prepare procedure call statement */
/* Handle Initialization code skipped */
OCIStmtPrepare(STMH, ERRH, stmt, strlen(stmt), OCI_NTV_SYNTAX, OCI_DEFAULT);
/* Bind procedure arguments */
inds[0] = 0;
strcpy((char *) arg1, "Hello World");
rlens[0] = strlen(arg1);
OCIBindByPos(STMH, &BNDH[0], ERRH, 1, (dvoid *) arg1, 20, SQLT_CHR,
(dvoid *) &(inds[0]), &(rlens[0]), &(rcode[0]), 0, (ub4 *) 0,
OCI_DEFAULT);
inds[1] = -1;
OCIBindByPos(STMH, &BNDH[1], ERRH, 1, (dvoid *) arg2, 20, SQLT_CHR,
(dvoid *) &(inds[1]), &(rlens[1]), &(rcode[1]), 0, (ub4 *) 0,
OCI_DEFAULT);
inds[2] = 0;
rlens[2] = 0;
OCIDescriptorAlloc(ENVH, (dvoid **) &rset, OCI_DTYPE_RSET, 0, (dvoid **) 0);
OCIBindByPos(STMH, &BNDH[2], ERRH, 2, (dvoid *) rset, 0, SQLT_RSET,
(dvoid *) &(inds[2]), &(rlens[2]), &(rcode[2]),
0, (ub4 *) 0, OCI_DEFAULT);
/* Execute procedure */
OCIStmtExecute(SVCH, STMH, ERRH, 1, 0, (CONST OCISnapshot *) 0,
(OCISnapshot *) 0, OCI_DEFAULT);
/* Convert result set to statement handle */
OCIResultSetToStmt(rset, ERRH);
rstmt = (OCIStmt *) rset;
/* After this the user can fetch from rstmt */
/* Issue get_next_result_set call to get handle to next_result set */
/* Prepare Get next result set procedure call */
OCIStmtPrepare(STMH, ERRH, n_rs_stm, strlen(n_rs_stm), OCI_NTV_SYNTAX,
OCI_DEFAULT);
/* Bind return value */
OCIBindByPos(STMH, &BNDH[1], ERRH, 1, (dvoid *) rset, 0, SQLT_RSET,
(dvoid *) &(inds[1]), &(rlens[1]), &(rcode[1]),
0, (ub4 *) 0, OCI_DEFAULT);
/* Execute statement to get next result set*/
OCIStmtExecute(SVCH, STMH, ERRH, 1, 0, (CONST OCISnapshot *) 0,
(OCISnapshot *) 0, OCI_DEFAULT);
/* Convert next result set to statement handle */
OCIResultSetToStmt(rset, ERRH);
rstmt = (OCIStmt *) rset;
/* Now rstmt will point to the second result set returned by the
remote stored procedure */
/* Repeat execution of get_next_result_set to get the output arguments */
Assume that the table loc_emp is a local table exactly like the Teradata emp table. The same assumption applies for loc_dept. outargs is a table with columns corresponding to the out arguments of the Teradata stored procedure.
create or replace package rcpackage is type RCTYPE is ref cursor; end rcpackage; /
declare
rc1 rcpackage.rctype;
rec1 loc_emp%rowtype;
rc2 rcpackage.rctype;
rec2 loc_dept%rowtype;
rc3 rcpackage.rctype;
rec3 outargs%rowtype;
out_arg varchar2(255);
begin
-- Execute procedure
out_arg := null; refcurproc@TERA('Hello World', out_arg, rc1);
-- Fetch 20 rows from the remote emp table and insert them into loc_emp
for i in 1 .. 20 loop
fetch rc1 into rec1;
insert into loc_emp (rec1.empno, rec1.ename, rec1.job,
rec1.mgr, rec1.hiredate, rec1.sal, rec1.comm, rec1.deptno);
end loop;
-- Close ref cursor
close rc1;
-- Get the next result set returned by the stored procedure
rc2 := dbms_hs_result_set.get_next_result_set@TERA;
-- Fetch 5 rows from the remote dept table and insert them into loc_dept
for i in 1 .. 5 loop
fetch rc2 into rec2;
insert into loc_dept values (rec2.deptno, rec2.dname, rec2.loc);
end loop;
--Close ref cursor
close rc2;
-- Get the output arguments from the remote stored procedure
-- Since we are in sequential mode, they will be returned in the
-- form of a result set
rc3 := dbms_hs_result_set.get_next_result_set@TERA;
-- Fetch them and insert them into the outarguments table
fetch rc3 into rec3;
insert into outargs (rec3.outarg, rec3.retval);
-- Close ref cursor
close rc3;
end;
/
This feature allows the gateway to optionally run in CHAR Semantics mode. Rather than always describing Teradata CHAR columns as CHAR(n BYTE), this feature describes them as CHAR(n CHAR) and VARCHAR(n CHAR). The concept is similar to Oracle database CHAR Semantics. You need to specify HS_NLS_LENGTH_SEMANTICS=CHAR to activate this option. Refer to Appendix D for more detail.
This feature optionally suppresses the ratio expansion from Teradata database to Oracle databases involving a multi-byte character set (for example, from US7ASCII to AL32UTF8, or from KO16MSWIN949 to KO16KSC5601). By default, Oracle gateways assume the worst ratio to prevent data being truncated or allocation of buffer with insufficient size. However, if you have specific knowledge of your Teradata database and do not want the expansion to occur, you can specify HS_KEEP_REMOTE_COLUMN_SIZE parameter to suppress the expansion. Refer to Appendix D for more detail.
Besides full IPv6 support between Oracle databases and the gateway, IPv6 is also supported between this gateway and Teradata. Refer to HS_FDS_CONNECT_INFO parameter in Appendix D for more detail.
You can optionally choose to terminate long idle gateway sessions automatically with the gateway parameter HS_IDLE_TIMEOUT. Specifically, when a gateway session is idle for more than the specified time limit, the gateway session is terminated with any pending changes rolled back.
Teradata and Oracle databases function differently in some areas, causing compatibility problems. The following compatibility issues are described in this section:
The Oracle concept of a schema does not exist in Teradata. A schema name included in a query is recognized by Teradata as a database name. In the Oracle database, the schema of an object is identical to the owner of that object. However, when one retrieves or references an OWNER field in a Data Dictionary view such as ALL_TABLES, the OWNER field really is referencing a Teradata database name.
When querying data dictionary tables, the following results are returned:
ALL_* data dictionary tables, data for every Teradata database is returned. The Teradata database name is returned in the OWNER, INDEX_OWNER, or TABLE_OWNER column depending on the data dictionary table being referenced.
ALL_USERS data dictionary table, each Teradata database name is returned in the USERNAME column.
USER_* data dictionary tables, data for the default Teradata database is returned for the OWNER or TABLE_OWNER column depending on the data dictionary table being referenced. If a default Teradata database is not defined, the DBC Teradata system database is used.
Naming rule issues include the following:
Oracle and Teradata use different database object naming rules. For example, the maximum number of characters allowed for each object name can be different. Also, the use of single and double quotation marks, case sensitivity, and the use of alphanumeric characters can all be different.
The Oracle database defaults to uppercase unless you surround identifiers with double quote characters. For example, to refer to the Teradata table called emp, enter the name with double quote characters, as follows:
SQL> SELECT * FROM "emp"@TERA;
However, to refer to the Teradata table called emp in the Teradata database named Scott from an Oracle application, enter the following:
SQL> SELECT * FROM "Scott"."emp"@TERA;
If the Teradata table called emp in the Teradata database named SCOTT, a name consisting entirely of uppercase letters, you can enter the owner name without double quote characters, as follows:
SQL> SELECT * FROM SCOTT."emp"@TERA;
or
SQL> SELECT * FROM scott."emp"@TERA;
Oracle recommends that you surround all Teradata object names with double quote characters and use the exact letter case for the object names as they appear in the Teradata data dictionary. This convention is not required when referring to the supported Oracle data dictionary tables or views listed in Appendix C, "Data Dictionary".
If existing applications cannot be changed according to these conventions, create views in Oracle to associate Teradata names to the correct letter case. For example, to refer to the Teradata table emp from an existing Oracle application by using only uppercase names, define the following view:
SQL> CREATE VIEW EMP (EMPNO, ENAME, SAL, HIREDATE)
AS SELECT "empno", "ename", "sal", "hiredate"
FROM "emp"@TERA;
With this view, the application can issue statements such as the following:
SQL> SELECT EMPNO, ENAME FROM EMP;
Using views is a workaround solution that duplicates data dictionary information originating in the Teradata data dictionary. You must be prepared to update the Oracle view definitions whenever the data definitions for the corresponding tables are changed in the Teradata database.
Data type issues include the following:
Oracle SQL uses hexadecimal digits surrounded by single quotes to express literal values being compared or inserted into columns defined as data type RAW.
This notation is not converted to syntax compatible with the Teradata VARBINARY and BINARY data types (a ff surrounded by single quotes followed by hexadecimal digits).
For example, the following statement is not supported:
SQL> INSERT INTO BINARY_TAB@TERA VALUES ('ff'xb)
where BINARY_TAB contains a column of data type VARBINARY or BINARY. Use bind variables when inserting into or updating VARBINARY and BINARY data types.
Teradata does not support implicit date conversions. Such conversions must be explicit.
For example, the gateway issues an error for the following SELECT statement:
SELECT DATE_COL FROM TEST@TERA WHERE DATE_COL = "1-JAN-2001";
To avoid problems with implicit conversions, add explicit conversions, as in the following:
SELECT DATE_COL FROM TEST@TERA WHERE DATE_COL = TO_DATE("1-JAN-2001")
Query issues include the following:
Teradata evaluates a query condition for all selected rows before returning any of the rows. If there is an error in the evaluation process for one or more rows, no rows are returned even though the remaining rows satisfy the condition.
Oracle evaluates the query condition row-by-row and returns a row when the evaluation is successful. Rows are returned until a row fails the evaluation.
For VARCHAR bind variables, the gateway passes empty bind variables to the Teradata database as a NULL value.
The locking model for an Teradata database differs significantly from the Oracle model. The gateway depends on the underlying Teradata behavior, so the following possible scenarios can affect Oracle applications that access Teradata through the gateway:
Read access might block write access.
Write access might block read access.
Statement-level read consistency is not guaranteed.
|
See Also: Teradata documentation for information about the Teradata locking model. |
If you encounter incompatibility problems not listed in this section or in "Known Problems", contact Oracle Support Services. The following section describes the known restrictions and includes suggestions for dealing with them when possible:
The gateway cannot guarantee transactional integrity in the following cases:
When a statement that is processed by the gateway causes an implicit commit in the target database
When the target database is configured to work in autocommit mode
|
Note: Oracle strongly recommends the following:
|
The gateway does not support savepoints. If a distributed update transaction is under way involving the gateway and a user attempts to create a savepoint, the following error occurs:
ORA-02070: database dblink does not support savepoint in this context
By default, the gateway is configured as COMMIT_CONFIRM and it is always the commit point site when the Teradata database is updated by the transaction.
Any COMMIT or ROLLBACK issued in a PL/SQL cursor loop closes all open cursors, which can result in the following error:
ORA-1002: fetch out of sequence
To prevent this error, move the COMMIT or ROLLBACK statement outside the cursor loop.
Oracle recommends that you place a DDL statement in its own transaction when executing such a statement with the pass-through feature. An explicit COMMIT must be issued after the DDL statement.
If the SQL statements being passed through the gateway result in an implicit commit at the Teradata database, the Oracle transaction manager is unaware of the commit and an Oracle ROLLBACK command cannot be used to roll back the transaction.
You cannot compare columns of data type TIME or TIMESTAMP to a bind variable.
The following SQL statement causes an error message:
SQL> select time_column from time_table@TERA where time_column = :a;
The following error is issued:
Invalid operation on an ANSI Datetime or Interval value.
This section lists restrictions on the following SQL syntax:
|
See Also: Appendix B, "Supported SQL Syntax and Functions" for more information about restrictions on SQL syntax. |
UPDATE and DELETE statements with the WHERE CURRENT OF clause are not supported by the gateway because they rely on the Oracle ROWID implementation. To update or delete a specific row through the gateway, a condition style WHERE clause must be used.
The EXPLAIN PLAN statement is not supported.
SQL statements that require the gateway to callback to Oracle database are not supported.
The following categories of SQL statements will result in a callback:
Any DML with a sub-select, which refers to a table in Oracle database. For example:
INSERT INTO emp@TERA SELECT * FROM oracle_emp;
Any DELETE, INSERT, UPDATE or "SELECT... FOR UPDATE..." SQL statement containing SQL functions or statements that needs to be executed at the originating Oracle database.
These SQL functions include USER, USERENV, and SYSDATE; and invovle the selection of data from the originating Oracle database. For example:
DELETE FROM emp@TERA WHERE hiredate > SYSDATE;
SELECT ename FROM tkhoemp@TERA WHERE hiredate IN (SELECT hiredate FROM oracle_emp) FOR UPDATE OF empno;
Any SQL statement that involves a table in Oracle database, and a LONG or LOB column in a remote table. For example:
SELECT a.long1, b.empno FROM scott.table@TERA a, emp b WHERE a.id=b.empno;
SELECT a.long1, b.dummy FROM table_non@TERA a, dual b;
where a.long1 is a LONG column.
You need to use double quotes to wrap around lowercase table names.
For example:
copy from tkhouser/tkhouser@inst1 insert loc_tkhodept using select * from "tkhodept"@TERA;
The gateway is not a shared server process and cannot support shared database links. Each gateway session spawns a separate gateway process and connections cannot be shared.
This section describes known problems and includes suggestions for correcting them when possible. If you have any questions or concerns about the problems, contact Oracle Support Services. A current list of problems is available online. Contact your local Oracle office for information about accessing the list.
The following known problems are described in this section:
The following restrictions apply when using LONG VARCHAR data types:
An unsupported SQL function cannot be used in a SQL statement that accesses a column defined as Teradata data type LONG VARCHAR.
You cannot use SQL*Plus to select data from a column defined as Teradata data type LONG VARCHAR when the data is greater than 80 characters in length. Oracle recommends using Pro*C or Oracle Call Interface to access such data in a Teradata database.
LONG VARCHAR data types must be NULLABLE for INSERT or UPDATE to work.
A table including a LONG VARCHAR column must have a unique index defined on the table or the table must have a separate column that serves as a primary key.
LONG VARCHAR data cannot be read through pass-through queries.
The gateway does not support the PL/SQL function COLUMN_VALUE_LONG of the DBMS_SQL package.
|
See Also: Appendix B, "Supported SQL Syntax and Functions" for more information about restrictions on SQL syntax. |
If you do not prefix a Teradata database object with its schema name in a SQL statement within a PL/SQL block, the following error message occurs:
ORA-6550 PLS-201 Identifier table_name must be declared.
Change the SQL statement to include the schema name of the object.