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. 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. 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 IO 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. Rman Create Standby From Active Database Objects' title='Rman Create Standby From Active Database Objects' />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. Rman Create Standby From Active Database Objects' title='Rman Create Standby From Active Database Objects' />Enqueues are shared memory structures locks that serialize access to database resources. They can be associated with a session or transaction. Recent Posts. ORA01580 error creating control backup file xxx, ORA27040 file create error, unable to create file RMAN failed to connect target database with ORA. Creating a Physical Standby using RMAN DUPLICATE FROM ACTIVE DATABASE. All you need to know about setting up GoldenGate ActiveActive Database Replication with Conflict Detection and Resolution. Golden gate oracle replication. However, note that this clause is intended for use only on a test database. It is not advisable to use this clause on a production database, because. 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 DBRECOVERYFILEDEST specifies the default location for the fast recovery area. DBRECOVERYFILEDESTSIZE specifies in bytes the hard limit on the total space to be used by database recovery files created in the recovery area location. The Oracle Suggested Backup Strategy described in the Oracle Database 2 Day DBA recommends using the fast recovery area as the primary location for recovery. 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 SQLPlus 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. Use a Fast Recovery Area. When configuring and enabling Flashback Database Know your application performance baseline before you enable flashback to help determine the overhead and to assess the application workload implications of turning on flashback database. Ensure the fast recovery area space is sufficient to hold the flashback database flashback logs. For more information about sizing the fast recovery area, see the Oracle Database Backup and Recovery Users 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 DBFLASHBACKRETENTIONTARGET to 2. GB of redo in a day, then a rule of thumb is to allow 2. GB to 3. 0 GB disk space for the flashback logs. 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 VFLASHBACKDATABASESTAT. ESTIMATEDFLASHBACKSIZE. Note that the DBFLASHBACKRETENTIONTARGET is a target and there is no guarantee that you can flashback the database that far. 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 Users Guide. To guarantee a flashback point in time you must use guaranteed restore points. Set the Oracle Enterprise Manager monitoring metric, Recovery Area Free Space for proactive alerts of space issues with the fast recovery area. Ensure there is sufficient IO bandwidth to the fast recovery area. Insufficient IO bandwidth with flashback database on is usually indicated by a high occurrence of the FLASHBACK BUF FREE BY RVWR wait event in an Automatic Workload Repository AWR report. Set the LOGBUFFER initialization parameter to at least 8 MB to give flashback database more buffer space in memory. For large databases with more than a 4. GB SGA, you may consider setting LOGBUFFER to values in the range of 3. MB for more information about LOGBUFFER and valid values on 3. Oracle Database Reference. Set the parameter PARALLELEXECUTIONMESSAGESIZE to at least 8. This improves the media recovery phase of any flashback database operation. If you have a Data Guard standby database, always set DBFLASHBACKRETENTIONTARGET to the same value on the standby databases as the primary. Active Speakers For Home Dj Free more. Set DBFLASHBACKRETENTIONTARGET initialization parameter to the largest value prescribed by any of the following conditions that apply To leverage flashback database to reinstate your failed primary database after Data Guard failover, for most cases set DBFLASHBACKRETENTIONTARGET to a minimum of 6. Consider cases where there are multiple outages, for example, first a network outage, followed later by a primary database outage, that may result in a transport lag between primary and standby database at failover time. For such cases set DBFLASHBACKRETENTIONTARGET to a value equal to the sum of 6.