17 Topics for Database Administrators and Developers

Privilege and Role Authorization

In general, database access control involves restricting data access and database activities. For example, you can restrict users from querying specified tables or executing specified database commands.

A user privilege is the right to run specific SQL statements. Privileges can be divided into the following categories:

• System privilege

  This is the right to perform a specific action in the database, or perform an action on any objects of a specific type. For example, CREATE USER and CREATE SESSION are system privileges.

• Object privilege

  This is the right to perform a specific action on an object, for example, query the employees table. Privilege types are defined by the database.

Privileges are granted to users at the discretion of other users. Administrators should grant privileges to users so they can accomplish tasks required for their jobs. Good security practice involves granting a privilege only to a user who requires that privilege to accomplish the necessary work.

A role is a named group of related privileges that you grant to users or other roles. A role helps manage privileges for a database application or user group.

Figure 17-1 depicts a common use for roles. The roles PAY_CLERK, MANAGER, and REC_CLERK are assigned to different users. The application role ACCTS_PAY, which includes the privilege to execute the ACCTS_PAY application, is assigned to users with the PAY_CLERK and MANAGER role. The application role ACCTS_REC, which includes the privilege to execute the ACCTS_REC application, is assigned to users with the REC_CLERK and MANAGER role.

Figure 17-1 Common Uses for Roles

Description of "Figure 17-1 Common Uses for Roles"

Profiles

In the context of system resources, a profile is a named set of resource limits and password parameters that restrict database usage and instance resources for a user. Profiles can limit the number of concurrent sessions for a user, CPU processing time available for each session, and amount of logical I/O available (see "Buffer I/O"). For example, the clerk profile could limit a user to system resources required for clerical tasks.

Profiles provide a single point of reference for users that share a set of attributes. You can assign a profile to one set of users, and a default profile to all others. Each user has at most one profile assigned at any point in time.

Network Encryption

Network encryption refers to encrypting data as it travels across the network between a client and server. An intruder can use a network packet sniffer to capture information as it travels on the network, and then spool it to a file for malicious use. Encrypting data on the network prevents this sort of activity.

Transparent Data Encryption

Oracle Advanced Security transparent data encryption enables you to encrypt individual table columns or a tablespace. When a user inserts data into an encrypted column, the database automatically encrypts the data. When users select the column, the data is decrypted. This form of encryption is transparent, provides high performance, and is easy to implement.

Transparent data encryption includes industry-standard encryption algorithms such as the Advanced Encryption Standard (AES) and built-in key management.

Oracle Database Vault

Oracle Database Vault is a security option that restricts privileged user access to application data. You can use Oracle Database Vault to control when, where, and how the databases, data, and applications are accessed. Thus, you can address common security problems such as protecting against insider threats, complying with regulatory requirements, and enforcing separation of duty.

Virtual Private Database (VPD)

Virtual Private Database (VPD) enables you to enforce security at the row and column level. A security policy establishes methods for protecting a database from accidental or malicious destruction of data or damage to the database infrastructure.

VPD is useful when security protections such as privileges and roles are not sufficiently fine-grained. For example, you can allow all users to access the employees table, but create security policies to restrict access to employees in the same department as the user.

Essentially, the database adds a dynamic WHERE clause to a SQL statement issued against the table, view, or synonym to which an Oracle VPD security policy was applied. The WHERE clause allows only users whose credentials pass the security policy to access the protected data.

Oracle Label Security (OLS)

Oracle Label Security (OLS) is a security option that enables you to assign data classification and control access using security labels. You can assign a label to both data and users.

When assigned to data, the label can be attached as a hidden column to existing tables, providing transparency to existing SQL. For example, rows that contain highly sensitive data can be labeled HIGHLY SENSITIVE, while rows that are less sensitive can be labeled SENSITIVE, and so on. When a user attempts to access data, OLS compares the user label with the data label and determines whether access should be granted. Unlike VPD, OLS provides an out-of-the-box security policy and the metadata repository for defining and storing labels.

Database Auditing

Database auditing is the monitoring and recording of selected user database actions. You can use standard auditing to audit SQL statements, privileges, schemas, objects, and network and multitier activity. Alternatively, you can use fine-grained auditing to monitor specific database activities, such as actions on a database table or times that activities occur. For example, you can audit a table accessed after 9:00 p.m.

Reasons for using auditing include:

• Enabling future accountability for current actions

• Deterring users (or others, such as intruders) from inappropriate actions based on their accountability

• Investigating, monitoring, and recording suspicious activity

• Addressing auditing requirements for compliance

Oracle Audit Vault

Oracle Audit Vault enables you to consolidate, report, and configure alerts for audited data. You can consolidate audit data generated by Oracle Database and other relational databases. You can also use Oracle Audit Vault to monitor audit settings on target databases.

Enterprise Manager Auditing Support

Oracle Enterprise Manager (Enterprise Manager) enables you to view and configure audit-related initialization parameters. Also, you can administer objects when auditing statements and schema objects. For example, Enterprise Manager enables you to display and search for the properties of current audited statements, privileges, and objects. You can enable and disable auditing as needed.

Site Failures

A site failure occurs when an event causes all or a significant portion of an application to stop processing or slow to an unusable service level. A site failure may affect all processing at a data center, or a subset of applications supported by a data center. Examples include an extended site-wide power or network failure, a natural disaster making a data center inoperable, or a malicious attack on operations or the site.

The simplest form of protection against site failures is to create database backups using RMAN and store them offsite. You can restore the database to another host. However, this technique can be time-consuming, and the backup may not be current. Maintaining one or more standby databases in a Data Guard environment enables you to provide continuous database service if the production site fails.

Computer Failures

A computer failure outage occurs when the system running the database becomes unavailable because it has shut down or is no longer accessible. Examples of computers failures include hardware and operating system failures.

The following Oracle features protect against or help respond to computer failures:

• Enterprise Grids

  In an Oracle Real Applications Cluster (Oracle RAC) environment, Oracle Database runs on two or more systems in a cluster while concurrently accessing a single shared database. A single database system spans multiple hardware systems yet appears to the application as a single database. See "Overview of Grid Computing".

• Oracle Data Guard

  Data Guard enables you to maintain a copy of a production database, called a standby database, that can reside on a different continent or in the same data center. If the primary database is unavailable because of an outage, then Data Guard can switch any standby database to the primary role, minimizing downtime. See Oracle Data Guard Concepts and Administration.

• Oracle Restart

  Components in the Oracle Database software stack, including the database instance, listener, and Oracle ASM instance, can restart automatically after a component failure or whenever the database host computer restarts. Oracle Restart ensures that Oracle components are started in the proper order, in accordance with component dependencies. See Oracle Database Administrator's Guide to learn how to configure Oracle Restart.

• Fast Start Fault Recovery

  A common cause of unplanned downtime is a system fault or crash. The fast start fault recovery technology in Oracle Database automatically bounds database instance recovery time. See Oracle Database Performance Tuning Guide for information on fast start fault recovery.

Storage Failures

A storage failure outage occurs when the storage holding some or all of the database contents becomes unavailable because it has shut down or is no longer accessible. Examples of storage failures include the failure of a disk drive or storage array.

In addition to Oracle Data Guard, solutions for storage failures include the following:

• Oracle Automatic Storage Management (Oracle ASM)

  Oracle ASM is a vertically integrated file system and volume manager in the database kernel (see "Oracle Automatic Storage Management (Oracle ASM)"). Oracle ASM eliminates the complexity associated with managing data and disks, and simplifies mirroring and the process of adding and removing disks.

• Backup and recovery

  The Recovery Manager (RMAN) utility can back up data, restore data from a previous backup, and recover changes to that data up to the time before the failure occurred (see "Backup and Recovery").

Data Corruption

A data corruption occurs when a hardware, software or network component causes corrupt data to be read or written. For example, a volume manager error causes bad disk read or writes. Data corruptions are rare but can have a catastrophic effect on a database, and therefore a business.

In addition to Data Guard and Recovery Manager, Oracle Database supports the following forms of protection against data corruption:

• Lost write protection

  A data block lost write occurs when an I/O subsystem acknowledges the completion of the block write when the write did not occur. You can configure the database so that it records buffer cache block reads in the redo log. Lost write detection is most effective when used with Data Guard.

• Data block corruption detection

  A block corruption is a data block that is not in a recognized Oracle format, or whose contents are not internally consistent. Several database components and utilities, including RMAN, can detect a corrupt block and record it in V$DATABASE_BLOCK_CORRUPTION. If the environment uses a real-time standby database, then RMAN can automatically repair corrupt blocks.

• Data Recovery Advisor

  Data Recovery Advisor is an Oracle tool that automatically diagnoses data failures, determines and presents appropriate repair options, and executes repairs at the user's request.

Human Errors

A human error outage occurs when unintentional or malicious actions are committed that cause data in the database to become logically corrupt or unusable. The service level impact of a human error outage can vary significantly depending on the amount and critical nature of the affected data.

Much research cites human error as the largest cause of downtime. Oracle Database provides powerful tools to help administrators quickly diagnose and recover from these errors. It also includes features that enable end users to recover from problems without administrator involvement.

Oracle Database recommends the following forms of protection against human error:

• Restriction of user access

  The best way to prevent errors is to restrict user access to data and services. Oracle Database provides a wide range of security tools to control user access to application data by authenticating users and then allowing administrators to grant users only those privileges required to perform their duties (see "Overview of Database Security").

• Oracle Flashback Technology

  Oracle Flashback Technology is a family of human error correction features in Oracle Database. Oracle Flashback provides a SQL interface to quickly analyze and repair human errors. For example, you can perform:

  • Fine-grained surgical analysis and repair for localized damage

  • Rapid correction of more widespread damage

  • Recovery at the row, transaction, table, tablespace, and database level

• Oracle LogMiner

  Oracle LogMiner is a relational tool that enables online files to be read, analyzed, and interpreted using SQL (see "Oracle LogMiner").

System and Database Changes

Planned system changes occur when you perform routine and periodic maintenance operations and new deployments, including scheduled changes to the operating environment that occur outside of the organizational data structure in the database. Examples include adding or removing CPUs and cluster nodes (a node is a computer on which a database instance resides), upgrading system hardware or software, and migrating the system platform.

Oracle Database provides dynamic resource provisioning as a solution to planned system and database changes:

• Dynamic reconfiguration of the database

  Oracle Database dynamically accommodates various changes to hardware and database configurations, including adding and removing processors from an SMP server and adding and remove storage arrays using Oracle ASM. For example, Oracle Database monitors the operating system to detect changes in the number of CPUs. If the CPU_COUNT initialization parameter is set to the default, then the database workload can dynamically take advantage of newly added processors.

• Autotuning memory management

  Oracle Database uses a noncentralized policy to free and acquire memory in each subcomponent of the SGA and the PGA. Oracle Database autotunes memory by prompting the operating system to transfer granules of memory to components that require it. See "Memory Management".

• Automated distributions of data files, control files, and online redo log files

  Oracle ASM automates and simplifies the layout of data files, control files, and log files by automatically distributing them across all available disks. See Oracle Automatic Storage Management Administrator's Guide to learn more about Oracle ASM.

Data Changes

Planned data changes occur when there are changes to the logical structure or physical organization of Oracle Database objects. The primary objective of these changes is to improve performance or manageability. Examples include table redefinition, adding table partitions, and creating or rebuilding indexes.

Oracle Database minimizes downtime for data changes through online reorganization and redefinition. This architecture enables you to perform the following tasks when the database is open:

• Perform online table redefinition, which enables you to make table structure modifications without significantly affecting the availability of the table

• Create, analyze, and reorganize indexes (see Chapter 3, "Indexes and Index-Organized Tables")

• Move table partitions (see "Overview of Partitions")

Application Changes

Planned application changes may include changes to data, schemas, and programs. The primary objective of these changes is to improve performance, manageability, and functionality. An example is an application upgrade.

Oracle Database supports the following solutions for minimizing application downtime required to make changes to an application's database objects:

• Rolling patch updates

  Oracle Database supports the application of patches to the nodes of an Oracle RAC system in a rolling fashion. See Oracle Database High Availability Best Practices.

• Rolling release upgrades

  Oracle Database supports the installation of database software upgrades, and the application of patchsets, in a rolling fashion—with near zero database downtime—by using Data Guard SQL Apply and logical standby databases. See Oracle Database Upgrade Guide.

• Edition-based redefinition

  Edition-based redefinition enables you to upgrade the database objects of an application while the application is in use, thus minimizing or eliminating down time. Oracle Database accomplishes this task by changing (redefining) database objects in a private environment known as an edition. See Oracle Database Advanced Application Developer's Guide.

• DDL with the default WAIT option

  DDL commands require exclusive locks on internal structures (see "DDL Locks"). In previous releases, DDL commands would fail if they could not obtain the locks. DDL specified with the WAIT option resolves this issue. See Oracle Database High Availability Overview.

• Creation of triggers in a disabled state

  You can create a trigger in the disabled state so that you can ensure that your code compiles successfully before you enable the trigger. See Oracle Database PL/SQL Language Reference.

Scalability

In a Database Server Grid, Oracle RAC enables you to add nodes to the cluster as the demand for capacity increases. The Cache Fusion technology implemented in Oracle RAC enables you to scale capacity without changing your applications. Thus, you can scale the system incrementally to save costs and eliminate the need to replace smaller single-node systems with larger ones.

You can incrementally add nodes to a cluster instead of replacing existing systems with larger nodes. Grid Plug and Play simplifies addition and removal of nodes from a cluster, making it easier to deploy clusters in a dynamically provisioned environment. Grid Plug and Play also enables databases and services to be managed in a location-independent manner. SCAN enables clients to connect to the database service without regard for its location within the grid.

Fault Tolerance

Fault tolerance is the protection provided by a high availability architecture against the failure of a component in the architecture. A key advantage of the Oracle RAC architecture is the inherent fault tolerance provided by multiple nodes. Because the physical nodes run independently, the failure of one or more nodes does not affect other nodes in the cluster.

Failover can happen to any node on the Grid. In the extreme case, an Oracle RAC system provides database service even when all but one node is down. This architecture allows a group of nodes to be transparently put online or taken offline, for maintenance, while the rest of the cluster continues to provide database service.

Oracle RAC provides built-in integration with Oracle Clients and connection pools. With this capability, an application is immediately notified of any failure through the pool that terminates the connection. The application avoids waiting for a TCP timeout and can immediately take the appropriate recovery action. Oracle RAC integrates the listener with Oracle Clients and the connection pools to create optimal application throughput. Oracle RAC can balance cluster workload based on the load at the time of the transaction.

Services

Oracle RAC supports services that can group database workloads and route work to the optimal instances assigned to offer the services. A service represents the workload of applications with common attributes, performance thresholds, and priorities.

You define and apply business policies to these services to perform tasks such as to allocate nodes for times of peak processing or to automatically handle a server failure. Using services ensures the application of system resources where and when they are needed to achieve business goals.

Services are integrated with the Database Resource Manager, which enables you to restrict the resources that are used by a service within an instance. In addition, Oracle Scheduler jobs can run using a service, as opposed to using a specific instance.

Data Warehouse Architecture (Basic)

Figure 17-3 shows a simple architecture for a data warehouse. End users directly access data that was transported from several source systems to the data warehouse.

Figure 17-3 Architecture of a Data Warehouse

Description of "Figure 17-3 Architecture of a Data Warehouse"

Figure 17-3 shows both the metadata and raw data of a traditional OLTP system and summary data. A summary is an aggregate view that improves query performance by precalculating expensive joins and aggregation operations and storing the results in a table. For example, a summary table can contain the sums of sales by region and by product. Summaries are also called materialized views.

Data Warehouse Architecture (with a Staging Area)

In the architecture shown in Figure 17-3, operational data must be cleaned and processed before being put into the warehouse. Figure 17-4 shows a data warehouse with a staging area, which is a place where data is preprocessed before entering the warehouse. A staging area simplifies the tasks of building summaries and managing the warehouse.

Figure 17-4 Architecture of a Data Warehouse with a Staging Area

Description of "Figure 17-4 Architecture of a Data Warehouse with a Staging Area"

Data Warehouse Architecture (with a Staging Area and Data Marts)

You may want to customize your warehouse architecture for different groups within your organization. You can achieve this goal by transporting data in the warehouse to data marts, which are independent databases designed for a specific business or project. Typically, data marts include many summary tables.

Figure 17-5 separates purchasing, sales, and inventory information into independent data marts. A financial analyst can query the data marts for historical information about purchases and sales.

Figure 17-5 Architecture of a Data Warehouse with a Staging Area and Data Marts

Description of "Figure 17-5 Architecture of a Data Warehouse with a Staging Area and Data Marts"

Analytic SQL

Oracle Database has introduced many SQL operations for performing analytic operations. These operations include ranking, moving averages, cumulative sums, ratio-to-reports, and period-over-period comparisons. For example, Oracle Database supports the following forms of analytic SQL:

• SQL for aggregation

  Aggregate functions such as COUNT return a single result row based on groups of rows rather than on single rows. Aggregation is fundamental to data warehousing. To improve aggregation performance in a warehouse, the database provides extensions to the GROUP BY clause to make querying and reporting easier and faster. See Oracle Database Data Warehousing Guide to learn about aggregation.

• SQL for analysis

  Analytic functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group. Oracle has advanced SQL analytical processing capabilities using a family of analytic SQL functions. For example, these analytic functions enable you to calculate rankings and percentiles and moving windows. See Oracle Database Data Warehousing Guide to learn about SQL for analysis and reporting.

• SQL for modeling

  With the MODEL clause, you can create a multidimensional array from query results and apply rules to this array to calculate new values. For example, you can partition data in a sales view by country and perform a model computation, as defined by multiple rules, on each country. One rule could calculate the sales of a product in 2008 as the sum of sales in 2006 and 2007. See Oracle Database Data Warehousing Guide to learn about SQL modeling.

OLAP

Oracle online analytical processing (OLAP) provides native multidimensional storage and rapid response times when analyzing data across multiple dimensions. OLAP enables analysts to quickly obtain answers to complex, iterative queries during interactive sessions.

Oracle OLAP has the following primary characteristics:

• Oracle OLAP is integrated in the database so that you can use standard SQL administrative, querying, and reporting tools.

• The OLAP engine runs within the kernel of Oracle Database.

• Dimensional objects are stored in Oracle Database in their native multidimensional format.

• Cubes and other dimensional objects are first class data objects represented in the Oracle data dictionary.

• Data security is administered in the standard way, by granting and revoking privileges to Oracle Database users and roles.

Oracle OLAP offers the power of simplicity: one database, standard administration and security, and standard interfaces and development tools.

Data Mining

Data mining involves automatically searching large stores of data for patterns and trends that go beyond simple analysis. Data mining uses sophisticated mathematical algorithms to segment data and evaluate the probability of future events. Typical applications of data mining include call centers, ATMs, E-business relational management (ERM), and business planning.

With Oracle Data Mining, the data, data preparation, model building, and model scoring results all remain in the database. Oracle Data Mining supports a PL/SQL API, a Java API, SQL functions for model scoring, and a GUI called Oracle Data Miner. Thus, Oracle Database provides an infrastructure for application developers to integrate data mining seamlessly with database applications.

Distributed SQL

Distributed SQL synchronously accesses and updates data distributed among multiple databases. An Oracle distributed database system can be transparent to users, making it appear as a single Oracle database.

Distributed SQL includes distributed queries and distributed transactions. The Oracle distributed database architecture provides query and transaction transparency. For example, standard DML statements work just as they do in a non-distributed database environment. Additionally, applications control transactions using the standard SQL statements COMMIT, SAVEPOINT, and ROLLBACK.

Database Links

A database link is a connection between two physical databases that enables a client to access them as one logical database. Oracle Database uses database links to enable users on one database to access objects in a remote database. A local user can access a link to a remote database without being a user on the remote database.

Figure 17-6 shows an example of user hr accessing the employees table on the remote database with the global name hq.example.com. The employees synonym hides the identity and location of the remote schema object.

Figure 17-6 Database Link

Description of "Figure 17-6 Database Link"

Oracle Streams Replication

In Oracle Streams replication, a change to a database object at one database can be shared with other databases in the replication environment. For example, Oracle Streams propagates an update to an employees table to an identical employees table in a different database. In this way, the database objects and data are kept synchronized at all databases in the replication environment.

Typical uses for Oracle Streams replication include:

• Creating a reporting site to offload processing from a primary OLTP site.

• Providing load balancing and improved scalability and availability for a call center or similar application.

• Providing site autonomy between locations to satisfy certain common business requirements.

• Transforming and consolidating data from multiple locations.

• Replicating data between different platforms and Oracle Database releases, and across a wide area network (WAN).

Oracle Streams Information Flow

The architecture of Oracle Streams is very flexible. Figure 17-7 depicts the basic information flow in a replication environment.

Figure 17-7 Oracle Streams Information Flow

Description of "Figure 17-7 Oracle Streams Information Flow"

As shown in Figure 17-7, Oracle Streams contains the following basic elements:

• Capture

  Oracle Streams can implicitly capture DML and DDL changes. Rules determine which changes are captured. Changes are formatted into logical change records (LCRs), which are messages with a specific format describing a database change.

• Staging

  LCRs are placed in a staging area, which is a queue that stores and manages captured messages. Message staging provides a holding area with security, as well as auditing and tracking of message data. Propagations can send messages from one queue to another. The queues can reside in the same or different databases.

• Consumption

  LCRs remain in a staging area until subscribers consume them implicitly or explicitly. An apply process implicitly applies changes encapsulated in LCRs.

Note:

Oracle Streams is fully inter-operational with materialized views, which you can use to maintain updatable or read-only copies of data (see "Overview of Materialized Views").

See Also:

Oracle Database 2 Day + Data Replication and Integration Guide to learn how to replicate data using Oracle Streams

Oracle Streams Advanced Queuing (AQ)

Oracle Streams Advanced Queuing (AQ) is a robust and feature-rich message queuing system integrated with Oracle Database. When an organization has different systems that must communicate with each other, a messaging environment can provide a standard, reliable way to transport critical information between these systems.

A sample use case is a business that enters orders in an Oracle database at headquarters. When an order is entered, the business uses AQ to send the order ID and order date to a database in a warehouse. These messages alert employees at the warehouse about the orders so that they can fill and ship them.

Message Queuing and Dequeuing

Advanced Queuing stores user messages in abstract storage units called queues. Enqueuing is the process by which producers place messages into queues. Dequeuing is the process by which consumers retrieve messages from queues.

Support for explicit dequeue allows developers to use Oracle Streams to reliably exchange messages. They can also notify applications of changes by leveraging the change capture and propagation features of Oracle Streams.

Figure 17-8 shows a sample application that explicitly enqueues and dequeues messages through Advanced Queuing, enabling it to share information with partners using different messaging systems. After being enqueued, messages can be transformed and propagated before being dequeued to the partner's application.

Figure 17-8 Oracle Streams Message Queuing

Description of "Figure 17-8 Oracle Streams Message Queuing"

Oracle Streams Use Case

For a sample use case, assume that a company uses Oracle Streams to maintain multiple copies of a corporate Web site. The business requirements include:

• A reporting database must contain the most current data for analysts in a New York office to perform ad hoc querying.

• Updatable materialized views must support the field sales staff.

• Data must be shared with applications hosted on a Sybase database.

Figure 17-9 illustrates this Streams configuration.

Figure 17-9 Streams Configuration

Description of "Figure 17-9 Streams Configuration"

Oracle Streams is used to replicate data in an n-way configuration consisting of sites in New York, London, and Tokyo. At each site, Streams implicit capture collects any changes that occur for subscribed tables in each local region, and stages them locally in the queue. Changes captured in each region are then forwarded to each of the other region's databases. Changes made at each database can be reflected at every other database, providing complete data for the subscribed objects throughout the world.

At each regional database, an Oracle Streams apply process applies the changes automatically. As changes are applied, Oracle Streams checks for and resolves any conflicts. Streams can also be used to exchange data for particular tables with non-Oracle databases. Using the Oracle Database Gateway for Sybase, a Streams apply process applies the changes to a Sybase database using the same mechanisms as it does for Oracle databases.

The reporting database is hosted in New York. This database is a fully functional Oracle database that has a read-only copy of the relevant application tables. The reporting site is not configured to capture changes on these application tables. Oracle Streams imposes no restrictions on the configuration or use of this reporting database.

The London site also serves as the master site for several updatable materialized view sites. Each salesperson receives an updatable copy of the required portion of data. These sites typically only connect once a day to upload their orders and download any changes made after their last refresh.