Creating multiple redo log copies

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Data Protection for SAP can save a number of copies of each redo log by using different IBM Storage Protect™ server management classes. By creating multiple redo-log copies on separate physical media, the administrator can restore and recover a database even if a backup tape becomes corrupted.

The following Data Protection for SAP profile file keywords are important for creating multiple redo log copies:
  • Keyword BRARCHIVEMGTCLASS denotes the IBM Storage Protect server management classes to be used when it saves redo logs. With the use of different management classes, the backup media that is targeted for redo logs is separated from the backup media that is targeted for the database objects. Different redo log copies can also be saved to different backup media.
  • Keyword REDOLOG_COPIES allows the administrator to initiate the creation of multiple backup copies of each redo log. By creating multiple copies on separate physical media, the database administrator is able to restore and recover databases in an SAP environment. The restore and recover can occur even if a backup tape becomes corrupted or lost.
  • Keyword MAX_SESSIONS specifies the maximum number of sessions that a single Data Protection for SAP instance is allowed to access to the IBM Storage Protect server.
These rules describe how Data Protection for SAP satisfies a request to back up redo log files:
  • Data Protection for SAP creates as many backup copies of each redo log as are specified by the REDOLOG_COPIES keyword.
  • Data Protection for SAP requires as many archive management classes that are defined by BRARCHIVEMGTCLASS as there are redo-log copies requested. To best protect against the loss of data, it is important that the different management classes are linked to different storage pools within IBM Storage Protect storage. This way, various redo log copies are on different backup media.
  • When RMAN is used, Data Protection for SAP requires that the maximum number of sessions that are defined by MAX_SESSIONS is greater than or equal to the number of redo log copies that are requested. A setup with a smaller number of sessions is not advised with the backint interface.
  • When SAP HANA is used, Data Protection for SAP HANA requires that the maximum number of sessions that are defined by MAX_SESSIONS is greater than or equal to the number of redo log copies that are requested. A setup with a smaller number of sessions is not advised with the backint interface.
  • Data Protection for SAP cannot control the order in which IBM Storage Protect processes the requests. Therefore, an administrator cannot rely on sessions to be processed in the order they were started by Data Protection for SAP.
  • When MAX_SESSIONS parameter is higher than SESSIONS value under server stanzas, Data Protection will enter a high performance mode and distribute the redo log copies across all usable server stanzas. However, when MAX_SESSIONS is equal or less than SESSIONS, Data Protection enters a high availability mode and redo log copies are distributed under first available stanza and defined archive management classes.
    Note: Keyword MAX_SESSIONS or optionally MAX_ARCH_SESSIONS specifies the maximum number of sessions.

SAP HANA might process redo logs while a database backup is still processing or several SAP HANA processes might run simultaneously. These combined sessions might exceed the number of available tape drives. To avoid this situation, save redo logs to disk storage pools and then move them to tape storage.