Configuring Oracle Database. This chapter describes best practices for configuring all Oracle databases, including single- instance, Oracle RAC databases, Oracle RAC One Node databases, and the primary and standby databases in Oracle Data Guard configurations (for more information about High Availability architectures, see Oracle Database High Availability Overview). Before trying to understand the functions of the database administrator, it is necessary to first learn the three different functional levels needed to maintain a. Security Management and Multi-Domain Security Management (Provider-1) delivers more security and control by segmenting your security management into multiple virtual. United States Check Point Software Technologies Inc. 959 Skyway Road Suite 300. Adopt these best practices to reduce or avoid outages, reduce the risk of corruption, and to improve recovery performance. Database Configuration High Availability and Fast Recoverability Best Practices. To reduce recovery time and increase database availability and redundancy: 5. Set the Database ARCHIVELOG Mode and FORCE LOGGING Mode. 14 Manageability. Oracle Database 10 g represents a major milestone in Oracle's drive toward self-managing databases. It automates many routine administrative tasks. 1Point2 2G International 2isys 3-Phase Measurements AS 3D Production Multimedia 3D Systems 3M Corporation 3M Deutschland GmbH 3View.Com Inc. 7-Technologies A/S. ![]() Running the database in ARCHIVELOG mode and using database FORCE LOGGING mode are prerequisites for database recovery operations. The ARCHIVELOG mode enables online database backup and is necessary to recover the database to a point in time later than what has been restored. Features such as Oracle Data Guard and Flashback Database require that the production database run in ARCHIVELOG mode. If you can isolate data that never needs to be recovered within specific tablespaces, then you can use tablespace level FORCELOGGING attributes instead of the database FORCELOGGING mode. Configure the Size of Redo Log Files and Groups Appropriately. Use Oracle log multiplexing to create multiple redo log members in each redo group, one in the data area and one in the Fast Recovery Area (unless the redo logs are in an Oracle ASM high redundancy disk group). This protects against a failure involving the redo log, such as a disk or I/O failure for one member, or a user error that accidentally removes a member through an operating system command. If at least one redo log member is available, then the instance can continue to function. To size redo log files and groups: Use a minimum of three redo log groups: this helps prevent the log writer process (LGWR) from waiting for a group to be available following a log switch. All online redo logs and standby redo logs are equal size. Use redo log size = 4. GB or redo log size > = peak redo rate x 2. Locate redo logs on high performance disks. Place log files in a high redundancy disk group, or multiplex log files across different normal redundancy disk groups, if using ASM redundancy. Note. Do not multiplex the standby redo logs. Use a Fast Recovery Area. The Fast Recovery Area is Oracle managed disk space that provides a centralized disk location for backup and recovery files. The Fast Recovery Area is defined by setting the following database initialization parameters: DB. When the fast recovery area is properly sized, files needed for repair are readily available. The minimum recommended disk limit is the combined size of the database, incremental backups, all archived redo logs that have not been copied to tape, and flashback logs. Enable Flashback Database. Flashback Database provides an efficient alternative to point- in- time recovery for reversing unwanted database changes. Flashback Database enables you to rewind an entire database backward in time, reversing the effects of database changes within a time window. The effects are similar to database point- in- time recovery (DBPITR). You can flash back a database by issuing a single RMAN command or a SQL*Plus statement instead of using a complex procedure. To enable Flashback Database, you configure a fast recovery area and set a flashback retention target. This retention target specifies how far back you can rewind a database with Flashback Database. For more information about specifying a fast recovery area, see Section 5. For more information about sizing the fast recovery area, see the Oracle Database Backup and Recovery User's Guide. A general rule of thumb is to note that the volume of flashback log generation is approximately the same order of magnitude as redo log generation. For example, if you intend to set DB. The same rule applies for guaranteed restore points. For example, if the database generates 2. GB redo every day, and if the guaranteed restore point will be kept for a day, then plan to allocate 2. GB. An additional method to determine fast recovery area sizing is to enable flashback database and allow the database to run for a short period (2- 3 hours). The estimated amount of space required for the fast recovery area can be retrieved by querying V$FLASHBACK. In some cases if there is space pressure in the fast recovery area where the flashback logs are stored then the oldest flashback logs may be deleted. For a detailed explanation of the fast recovery area deletion rules see the Oracle Database Backup and Recovery User's Guide. To guarantee a flashback point- in- time you must use guaranteed restore points. Set the Oracle Enterprise Manager monitoring metric, . Insufficient I/O bandwidth with flashback database on is usually indicated by a high occurrence of the . For large databases with more than a 4. GB SGA, you may consider setting LOG. This improves the media recovery phase of any flashback database operation. If you have a Data Guard standby database, always set DB. For such cases set DB. This ensures that the failed primary database can be flashed back to an SCN that precedes the SCN at which the standby became primary - a requirement for primary reinstatement. If using Flashback Database for fast point in time recovery from user error or logical corruptions, set DB. An example query to monitor progress is. In 1. 1. 2. 0. 2 there are significant performance enhancements to nearly eliminate any overhead when you first enable flashback database, and during batch direct loads. For more information, see . With the Fast- Start Fault Recovery feature, the FAST. This parameter specifies a target for the expected recovery time objective (RTO), which is the time, in seconds, that it should take to start the instance and perform cache recovery. When you set this parameter, the database manages incremental checkpoint writes in an attempt to meet the target. If you have chosen a practical value for this parameter, then you can expect your database to recover, on average, in approximately the number of seconds you have chosen. Initially, set the FAST. Data block corruption can damage internal Oracle control information or application and user data, leading to crippling loss of critical data and services. The Oracle Database corruption prevention, detection, and repair capabilities are built on internal knowledge of the data and transactions it protects, and on the intelligent integration of its comprehensive high availability solutions. For more information about recovery from data corruption, see Section 1. Database- wide logical corruptions caused by human or application errors can be undone with Oracle Flashback Technologies. Tools are also available for proactive validation of logical data structures. For example, the SQL*Plus ANALYZE TABLE statement detects inter- block corruptions. Preventing Widespread Data Corruption. To achieve the most comprehensive data corruption prevention and detection: Use Oracle Data Guard with physical standby databases to prevent widespread block corruption. Oracle Data Guard is the best solution for protecting Oracle data against data loss and corruption, and lost writes. For more information, see Section 9. Oracle highly recommends the minimum setting of DB. If the performance overhead of enabling DB. For more information, see Section 4. Using Oracle ASM redundancy for disk groups provides mirrored extents that can be used by the database if an I/O error or corruption is encountered. For continued protection, Oracle ASM redundancy provides the ability to move an extent to a different area on a disk if an I/O error occurs. The Oracle ASM redundancy mechanism is useful if you have bad sectors returning media sense errors. For more information, see Section 4. For more information about Active Data Guard, see Section 9. For more information, see Section 5. For more information, see Section 5. For more information, see Chapter 8, . You can also review all targets in a single view from the HA Console. For more information, see Chapter 1. See Section 5. 2. Use Enterprise Manager to manage and monitor your Data Guard configuration. By taking advantage of Automatic Block Media Recovery, a corrupt block found on either a primary database or a physical standby database can be fixed automatically when the Active Data Guard option is used. For more information about Automatic Block Media Recovery, see Section 1. After determining the corruptions, the table can be re- created or another action can be taken. Set DISK. However, for optimal performance, it is always a best practice to ensure that asynchronous I/O is actually being used. Query the V$IOSTAT. Refer to Chapter 9, . However, PGA. Huge. Pages is a feature integrated into the Linux kernel from release 2. This feature provides the alternative to the 4. K page size providing bigger pages. Using Huge. Pages has the benefit of saving memory resources by decreasing page table overhead while making sure the memory is not paged to disk. This contributes to faster overall memory performance. Next to this overall node stability will benefit from using Huge. Pages. Ensuring the entire SGA of a database instance is stored in Huge. Pages can be accomplished by setting the init. Setting this parameter will ensure that an instance will start only when it can get all of its memory for SGA from Huge. Pages. For this reason the setting use. This setting still ensures that Huge. Pages are used when available, but also ensures that ASM as part of Grid Infrastructure starts when Huge. Pages are not or insufficiently configured. Use Automatic Shared Memory Management, as Huge. Pages are not compatible with Automatic Memory Management. Disable Parallel Recovery for Instance Recovery. When the value of RECOVERY. This typically occurs with a very aggressive setting of FAST. In this case, set RECOVERY. Oracle Restart is used in single- instance environments only.
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