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.
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.
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.
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.
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.
A standby database is considered to be active if a Dbvisit process has run within the last DBV_LAST_RUN_OFFSET days to ship archive logs to this database from the primary.
Note the default value:
DBV_LAST_RUN_OFFSET=1
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:
If there are archive log files older than days to keep the archive log files, then delete these.
If there are more archive log files than Number of archive log files to keep, then delete these (oldest ones first).
If there are more archive logs that have been backed up by RMAN at least Number of times an archive log has to be backed up rman before being deleted times, then delete these.
If the Threshold in % of how much disk space may be used < mount point fullness criteria are met, then mark archives for deletion (oldest ones first). The number of archives marked for deletion is how many archive logs. The archives will only be deleted if Delete archive files once threshold is reached=Y. After deletion of the archives, and the criteria are still met (Threshold in % of how much disk space may be used < mount point fullness), then mark more archives for deletion (number of archives marked for deletion will be again HOWMANY_ARCHSOURCE, and oldest ones first). This process will continue until the criteria are no longer met.
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.
From the above screen shot the numbers 1 to 7 indicate the settings for managing oracle archive logs in the primary database, this is optional if you have your backup jobs that take care of deleting the archive logs , you can leave this setting disabled. Remember the archive logs must be retained for the dbvisit process to transfer it from primary tostandby. The setting indicated from number 8 to 12 are for managing the standby database archive logs.
GUI field names and DDC variables referrence:
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
Primary Archive Log Management by Dbvisit deletes own primary database archivelogs - so directly from Flash Recovery Area or log_archive_dest
( 1 ) Enable archive log management on primary: By default, this setting is set to No and you can enable it when you want Dbvisit to manage the archive logs from the primary database.
( 2 ) Number of archive logs to keep: Specifies the number of archive log files to keep on the primary server. Archive log files greater than this number will be removed (oldest first).To disable this setting, set it to 0. If you are not sure, set it to 0 (disable).
( 3 ) Days to keep archive log files: Specify the number of days to keep the archive log files on the primary server. If this value (in days) is reached, the archive log files will be removed from the server. To disable this setting, set it to 0, if you are not sure, set it to 7. Ensure that enough disk space is available to store the archive logs.
( 4 ) Number of times an archive log has to be backed up by RMAN before being deleted: Specify the number of times an archive log has to be backed up by RMAN before Dbvisit Standby deletes it from the primary server. To disable this setting, set it to 0 which is the default value.
( 5 ) Threshold in % of how much disk space may be used: Specifies the threshold in percentage (%) of how much disk space may be taken up by the archive log files on disk before an alert is triggered on the primary server. A value of 80 means at 80% space threshold is reached, an alert will be triggered. Please specify the threshold as an integer.
( 6 ) Threshold in % of how much FRA space may be used: Specifies the threshold in percentage (%) of how much FRA (flash/fast recovery area) space may be taken up by the archive log files on disk before an alert is triggered on the primary server. A value of 80 means at 80% FRA space threshold is reached, an alert will be triggered. Please specify the threshold as an integer.
( 7 ) Delete archive files once threshold is reached?: Specify if archive log files should be deleted once the percentage threshold (Threshold in % of how much disk space may be used) on the primary server is reached. Once the threshold is reached oldest archive log files are deleted first. By default, this is set as No and Multiplatform notification will send out an email or slack notification once this is reached if enabled.
There is no verification that these archive log files have been backed up. Dbvisit Standby does not perform backups, this should be configured outside the Dbvisit Standby product.
This setting has no influence on whether archive log files are deleted for the Number of archive logs to keep or Days to keep archive log files. These settings will delete archive log files once the percentage threshold is met.
Process Flow for Primary AMM:
5.2 Standby Archive Management Settings
Standby Archive Log Management by Dbvisit deletes transferred archivelogs in ARCHDEST location on standby server
( 8 ) Enable Archive Management on Standby: Specifies if the AMM module to manage the archive log files is turned on or off on the standby server. This is recommended to set to yes as it will manage the archive logs that are shipped from primary to standby’s Archive log destination location(ARCHDEST).
( 9 ) Number of archive log files to keep: Specifies the number of archive log files to keep on the standby server. Archive log files greater than this number will be removed (oldest first).To disable this setting, set to 0. If you are not sure, set to 0 (disable).
( 10 ) Days to keep archive log files: Specifies the number of days to keep the archive log files on the standby server. After this, the archive log files will be removed from the server. This is specific to the archive log destination location in standby from which the archivelog is applied. The archive logs are sent from primary to standby.
( 11 ) Threshold in % of how much disk space may be used: Specifies the threshold in percentage (%) of how much disk space may be taken up by the archive log files on disk before an alert is triggered on the standby server.
( 12 ) Delete archive files once threshold is reached?: Specifies if the archive log files should be deleted once the percentage threshold (THRESHOLD_ARCHDEST) on the standby server is reached. Once the threshold is reached the oldest archive log files are deleted first.
There is no verification that these archive log files have been backed up, this (backups) is outside the scope of Dbvisit Standby
This setting has no influence on whether archive log files are deleted for Days to keep archive log files or Number of archive log files to keep. These settings will delete archive log files once the percentage threshold is met.
Flow of standby AMM process:
Below is an example of the archive log management settings from both primary and standby. In this example we have set for both primary and standby. We recommend checking the archive logs and database backup schedules and deletion frequencies before enabling this in the primary.
