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 ODBC. 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 OPEN_CURSORS initialization parameter of Oracle database |
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, READ_ONLY_AUTOCOMMIT, SINGLE_SITE, 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 access to the non-Oracle database that do not have logging.
SINGLE_SITE_AUTOCOMMIT provides read and write access to the non-Oracle database which do not have logging. Any update is committed immediately, and the gateway cannot participate in distributed updates.
| 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 which 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=dsn_value
where, dsn_value on Microsoft Windows, is the name of the system DSN defined in the Microsoft Windows ODBC Data Source Administrator and on UNIX based system, it is data source name configured in the odbc.ini file.
The entry for dsn_value is case sensitive.
| 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 | 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 | None |
| Range of Values | Not applicable |
Specifies the full path name to the ODBC driver manager.
This is a required parameter, whose format is:
HS_FDS_SHAREABLE_NAME=odbc_installation_path/lib/libodbc.sl
Where:
odbc_installation_path is the path where the ODBC driver is installed.
This parameter applies only to UNIX based platforms.
| 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 | 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 adjust to correct 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 | 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 Oracle Database Gateway for ODBC 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)
E12070-03
January 2012
Oracle Database Gateway for ODBC User's Guide, 11g Release 2 (11.2)
E12070-03
Copyright © 2007, 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
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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 ODBC 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 non-Oracle systems.
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 Gateways, enable 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.
|
See Also: Oracle Database Heterogeneous Connectivity User's Guide for more information about Heterogeneous Services. |
Oracle Database Gateway for ODBC is intended for low-end data integration solutions requiring the dynamic query capability to connect from an Oracle database to non-Oracle systems. Any data source compatible with the ODBC standards described in this chapter can be accessed using Oracle Database Gateway for ODBC.
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.
To access the non-Oracle data store using Oracle Database Gateway for ODBC, the gateway works with an ODBC driver. The driver that you use must be on the same machine as the gateway. The non-Oracle system can reside on the same machine as the Oracle database or on a different machine.
The gateway can be installed on the machine running the non-Oracle system, the machine running the Oracle 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.
|
Note: The ODBC driver may require non-Oracle client libraries even if the non-Oracle database is located on the same machine. Refer to your ODBC driver documentation for information about the requirements for the ODBC driver. |
Figure 1-1 shows an example of a configuration in which an Oracle and non-Oracle database are on separate machines, communicating through Oracle Database Gateway for ODBC. The client connects to the non-Oracle system through a network.
Figure 1-1 Oracle and Non-Oracle Systems on Separate Machines
In this configuration:
A client connects to the Oracle database through Oracle Net.
The Heterogeneous Services component of the Oracle database connects through Oracle Net to the gateway.
The gateway communicates with the following non-Oracle components:
An ODBC driver manager
An ODBC driver
Each user session receives its own dedicated agent process spawned by the first use in that user session of the database link to the non-Oracle system. The agent process ends when the user session ends.
|
Note: The ODBC driver may require non-Oracle client libraries even if the non-Oracle database is located on the same machine. Refer to your ODBC driver documentation for information about the requirements for the ODBC driver. |
Figure 1-2 shows an example of a configuration in which an Oracle and non-Oracle database are on the same machine, again communicating through Oracle Database Gateway for ODBC.
Figure 1-2 Oracle and Non-Oracle Systems on the Same Machine
In this configuration:
A client connects to the Oracle database through Oracle Net.
The Heterogeneous Services component of the Oracle database connects through Oracle Net to the gateway
The agent communicates with the following non-Oracle components:
An ODBC driver manager
An ODBC driver
The driver then allows access to the non-Oracle data store.
Each user session receives its own dedicated agent process spawned by the first use in that user session of the database link to the non-Oracle system. The agent process ends when the user session ends.
|
Note: The ODBC driver may require non-Oracle client libraries even if the non-Oracle database is located on the same machine. Refer to your ODBC driver documentation for information about the requirements for the ODBC driver. |
To use Oracle Database Gateway for ODBC, you must have an ODBC driver installed on the same machine as the gateway. The ODBC driver manager and driver must meet the following requirements:
The following ODBC catalog functions must work inside a transaction:
SQLColumns
SQLForeignKeys
SQLGetFunctions
SQLGetInfo
SQLGetTypeInfo
SQLPrimaryKeys
SQLProcedureColumns
SQLProcedures
SQLStatistics
SQLTables
On Windows:
The ODBC driver must have compliance level to ODBC standard 3.0. For multi-byte support, the driver needs to meet ODBC standard 3.5.
The ODBC driver and driver manager must conform to ODBC application program interface (API) conformance Level 1 or higher. If the ODBC driver or driver manager does not support multiple active ODBC cursors, the complexity of SQL statements that you can execute using Oracle Database Gateway for ODBC is restricted.
On UNIX:
The ODBC driver manager must be installed on the same machine.
The ODBC driver must have compliance level to ODBC Standard 3.0 and have a conformance level 1 or higher. If the ODBC driver works with an ODBC driver manager, the ODBC driver manager must be compliant with ODBC Standard 3.0 or higher. The ODBC driver must have compliance level to ODBC standard 3.0. For multi-byte support, the driver needs to meet ODBC standard 3.5.
|
See Also: Your ODBC driver documentation for dependencies on an ODBC driver manager, and Oracle Database Concepts for more information on transaction isolation levels. |
The ODBC driver you use must support all of the core SQL ODBC data types and must support SQL grammar level SQL_92. The ODBC driver should also expose the following ODBC APIs:
SQLAllocHandle
SQLBindCol
SQLBindParameter
SQLCancel
SQLColAttribute
SQLColumns
SQLConnect
SQLDescribeCol
SQLDisconnect
SQLDriverConnect
SQLEndTran
SQLExecDirect
SQLExecute
SQLFetch
SQLForeignKeys
SQLFreeHandle
SQLFreeStmt
SQLGetConnectAttr
SQLGetData
SQLGetDiagField
SQLGetDiagRec
SQLGetEnvAttr
SQLGetFunctions
SQLGetInfo
SQLGetStmtAttr
SQLGetTypeInfo
SQLMoreResults
SQLNumResultCols
SQLParamData
SQLPrepare
SQLPrimaryKeys
SQLProcedureColumns
SQLProcedures
SQLPutData
SQLRowCount
SQLSetConnectAttr
SQLSetEnvAttr
SQLSetDescField
SQLSetDescRec
SQLSetStmtAttr
SQLStatistics - If statistics are to be supported
SQLTables
This appendix contains the following sections:
Oracle Database Gateway for ODBC supports the following statements, but only if the ODBC driver and non-Oracle system can execute them and if the statements contain supported Oracle SQL functions:
DELETE
INSERT
SELECT
UPDATE
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, for ALTER, CREATE, DROP, and GRANT statements, use the pass-through feature of the gateway if you need to use DDL statements against the non-Oracle system database.
|
Note: TRUNCATE cannot be used in a pass-through statement. |
|
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 the non-Oracle system can be used.
The INSERT statement is fully supported. However, only Oracle functions supported by the non-Oracle system 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 non-Oracle system after the gateway has converted them to the native SQL. Only a limited set of functions are assumed to be supported by the non-Oracle system. Most Oracle functions have no equivalent function in this limited set. Consequently, although post-processing is performed by the Oracle database, Oracle Database Gateway for ODBC does not support many Oracle functions, possibly impacting performance.
If an Oracle SQL function is not supported by Oracle Database Gateway for ODBC, this function is not supported in DELETE, INSERT, or UPDATE statements. In SELECT statements, these functions are evaluated by the Oracle database and processed after they are returned from the non-Oracle system.
If an unsupported function is used in a DELETE, INSERT, or UPDATE statement, it generates the following Oracle error:
ORA-02070: database db_link_name does not support function in this context
Oracle Database Gateway for ODBC assumes that ODBC driver provider that is being used supports the following minimum set of SQL functions:
AVG(exp)
LIKE(exp)
COUNT(*)
MAX(exp)
MIN(exp)
NOT
This manual describes the Oracle Database Gateway for ODBC, which enables Oracle client applications to access non-Oracle systems 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 ODBC
Diagnosing gateway errors
Using the gateway to access non-Oracle system data
|
Note: You should understand the fundamentals of Oracle Database Gateways and the UNIX based platform before using this guide to install or administer the gateway. |
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Many of the examples in this book use the sample schemas of the seed database, which is installed by default when you install Oracle. Refer to Oracle Database Sample Schemas for information on how these schemas were created and how you can use them yourself.
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