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Archivelogs management is critical for maintaining your standby database in sync. It is very important to ensure that archivelogs which are not needed for backup or for synchronization are deleted. Dbvisit StandbyMP includes Automatic Archivelog Management (AMM) Module which is optional and helps you with this task.
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It is very important to consider proper Archivelog management, otherwise your standby database will run out of sync frequently, your primary backups will fail or you will run out of space on primary or standby server. |
1. AMM Concept
The Dbvisit Standby Archive Log Management Module (AMM) fully automates the management and monitoring of the Oracle database archive log space on the primary in lash recovery area or in log_archive_dest as well as the Dbvisit ARCHDEST location on the standby server.
By default when creating a new DDC file in version 10, the AMM module is disabled for the primary database. This is to ensure the Dbvisit AMM module does not interfere with archive log purging options implemented as part of RMAN backup strategies. We do however recommend that you leave at least one day worth of archive logs on the primary server and not delete all archive logs following a backup, as they may not have been transferred to the standby database server.
Unlike the Oracle database files location, the Oracle archive logs location needs to be monitored and managed constantly to ensure the database continues its optimal operation. If the disk space available to Oracle archive logs is used up, the whole database will "freeze" and not allow any update or insert operation.
Dbvisit Standby Archive Log Management Module includes the following options:
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Alerts through email when Oracle archive logs have reached a set threshold of available disk space.
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Can delete Oracle archive logs after a set number of days.
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Can ensure that only x number of Oracle archive log files remain on the server.
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Can delete Oracle archive logs after available disk space has been used up to ensure continual database operation.
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Ensures the Oracle archive logs have been sent to the standby database before removing any archive logs.
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AMM Module:
Is optional to use and it’s by default disabled on primary and standby
Without its configuration, archivelogs can eventually fill disk on standby server or even primary server
Can be enabled/disabled separately for primary and standby server
Can be set from dbvcontrol GUI and also by directly editing DDC file
2. Primary Database Archivelogs and AMM
There are three possible scenarios and approaches for primary database archivelog management when Dbvisit Synchronization is in place. If Dbvisit StandbyMP AMM is enabled, it deletes archivelogs directly from db_recovery_file_dest or log_archive_dest.A. primary database archivedlogs are already backed up and deleted by your existing backup tools.
In this case, all primary archivelogs are backed up and deleted by your existing backups. There’s no further action required, you can leave AMM disabled.
You must however ensure that your backup scripts leave sufficient amount of archivedlogs on primary server. Minimum retention we recommend is 1-2 hours. If you fail to maintain this retention (for example you would run RMAN> delete archivelog all;) your standby database will get out of synchronization.
B. primary database archivedlogs are not managed at all
This includes for example situations when your primary database wasn’t in archivelog mode prior to Dbvisit StandbyMP deployment. In this case, we would recommend you to enable AMM for primary as described further on this page.
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Dbvisit Standby is not replacing your backup scripts or backup software. It is important that you still backup your database and archive log to a different storage or a tape device. |
C. primary database archivedlogs are already backed up by your existing backup tools, but you want to leave the deletion to Dbvisit
In this case, all primary archivelogs are backed up by your existing backups, but you want to delegate the deletion of archivedlogs to Dbvisit StandbyMP AMM to prevent any risk of getting your standby database out-of-sync due to missing and delete archived log.
Dbvisit will never delete archivedlog which wasn’t transferred to standby server and you can also specify additional parameters which would prevent any undesired behavior.
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Archivelog deletion by AMM on primary is triggered only at the end of transfer process - and the transfer must finish successfully |
3. Standby Database Archivelogs and AMM
Archivelogs on standby server are Dbvisit specific and we recommed to enable AMM in every case. AMM should be always enabled for standby. AMM then deletes all archivedlogs from ARCHDEST location (ARCHDEST is specified during DDC creation). There are never any archivelogs placed in db_recovery_file_dest or log_archive_dest by Dbvisit StandbyMP.
4. Enable AMM on primary
We can enable AMM by accessing the Configuration ACTIONS:
2. AMM and Multiple Standby Databases
In the case of multiple standby databases, Dbvisit Standby checks if an archive log has been transferred to all active standby databases before deleting it on the primary.
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In this context, the cascade setup is also considered a multiple standby environment. That means the standby DB is considered to be a primary DB for the cascade standby DB. |
3. Dbvisit Standby AMM processing overview
The order of precedence in managing the archive log files are:
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If Delete archive files once threshold is reached=N, then only a warning email will be sent. No archives will be deleted when the Threshold in % of how much disk space may be used < mount point fullness criteria are met. Setting variable Delete archive files once threshold is reached=N has no influence over days to keep the archive log files and Number of archive log files to keep. These will still delete archive files when their criteria are met.
4. Dbvisit Standby AMM log file
The Dbvisit Standby Archive Log Management Module (AMM) produces a separate log file to the Dbvisit Standby database processing. The log file can be found in the same location as the Dbvisit Standby database log file. The log file is called <DDC>_arch_management.log. The location is determined by the LOGDIR and LOGDIR_DR settings in the DDC file.
5. Archivelog Management Settings (AMM)
This section provides an overview of the variables that can be configured for the AMM module with regards to the Primary Database. Unlike the previous versions, the archive log management module is completely separated from the DDC configurations and now can be edited directly from control center.
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Number | GUI Field Name | DDC variable | Values |
1 | Enable Archivelog Management on Primary | ARCHSOURCE_MANAGEMENT | Y or N |
2 | Number of archive log files to keep | NUM_ARCHSOURCE_TO_KEEP | whole numbers, 0 to disable |
3 | Days to keep the archive log files | DAYS_TO_KEEP_ARCHSOURCE | whole and decimal numbers, 0 to disable |
4 | Number of times an archive log has to be backed up by rman before being deleted | ARCHSOURCE_BACKUP_COUNT | whole numbers, 0 to disable |
5 | Threshold in % of how much disk space may be used | THRESHOLD_ARCHSOURCE | percent |
6 | Threshold in % of how much FRA space may be used | FRA_THRESHOLD_ARCHSOURCE | percent |
7 | Delete archive files once threshold is reached | DELETE_ARCHSOURCE_THRESHOLD | Y or N |
8 | Enable Archivelog Management on Standby | ARCHDEST_MANAGEMENT | Y or N |
9 | Number of archive log files to keep | NUM_ARCHDEST_TO_KEEP | whole numbers, 0 to disable |
10 | Days to keep the archive log files | DAYS_TO_KEEP_ARCHDEST | whole and decimal numbers, 0 to disable |
11 | Threshold in % of how much disk space may be used | THRESHOLD_ARCHDEST | percent |
12 | Delete archive files once threshold is reached | DELETE_ARCHDEST_THRESHOLD | Y or N |
5.1 Primary Archive Management Settings
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Primary Archive Log Management by Dbvisit deletes own primary database archivelogs - so directly from Flash Recovery Area or log_archive_dest |
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Process Flow for Primary AMM:
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5.2 Standby Archive Management Settings
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Standby Archive Log Management by Dbvisit deletes transferred archivelogs in ARCHDEST location on standby server |
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