FAQ-Standby-How to

HOW TO

1. How can you control when an archive log can be deleted in the standby database? In Oracle 11g, you can control it by using the log_auto_delete initialization parameter. The log_auto_delete parameter must be coupled with the log_auto_del_retention_target parameter to specify the number of minutes an archive log is maintained until it is purged. Default is 24 hours. For archivelog retention to be effective, the log_auto_delete parameter must be set to true.

2. In a logical Standby Data Guard configuration, how can you tell the dbms_scheduler to only run jobs in the primary database? Logical standby now provides support for DBMS_SCHEDULER. It is capable of running jobs in both primary and logical standby databases. You can use the DBMS_SCHEDULER.SET_ATTRIBUTE procedure to set the database_role. You can specify that the jobs can run only when operating in that particular database role.

3. If you have a low-bandwidth WAN network, what can you do to improve the data guard configuration in a GAP detected situation? It can be enabled using the compression parameter. Compression becomes enabled only when a gap exists and the standby database needs to catch up to the primary database. alter system set log_archive_dest_1='SERVICE=DBA11GDR COMPRESSION=ENABLE';

4. If you wanted to upgrade your current 10g physical standby data guard configuration to 11g, can you upgrade the standby to 11g first then upgrade the primary ? Yes, in Oracle 11g, you can temporarily convert the physical standby database to a logical standby database to perform a rolling upgrade. When you issue the convert command you need to keep the identity: alter database recover logical standby keep identity;

5. How would you delay an application of the logs to the physical standby mode?

* The standby gets naturally applied to the redo logs at the time of their arrival from the primary database.

* There are times when a time lag is needed to be created between archiving a redo log at the primary point and applying the log at standby.

* You need to modify the parameter for initialization on the primary site to lead to a delay on the standby site.

* For instance, if you want a delay of one hour, you can set a log for delay at sixty minutes. It is worth mentioning in this regard that the delay is always given in minutes in the format of, for instance, 60'.

* With this action, the redo logs are still copied from the primary to standby site but it does not immediately applied. They get applied after the expiry of the specific time interval that has been set.