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 (primary only, standby only, both enabled or both disabled)
Can be set from dbvcontrol GUI and also by directly editing DDC file

The Dbvisit StandbyMP 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.

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

2.1 Enable AMM on primary

We can enable AMM by accessing the ACTIONS right pane. You can use this example setting for your environment as well:

GUI field names and DDC variables referrence:

Number	GUI Field Name	DDC variable	Values and explanation
2	Enable Archivelog Management on Primary	ARCHSOURCE_MANAGEMENT	Y or N. This wholly disables or enables AMM module on primary. By default AMM on primary is disabled.
3	Number of archive log files to keep	NUM_ARCHSOURCE_TO_KEEP	whole numbers, 0 to disable 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). If you are not sure, set it to 0 (disable).
4	Days to keep the archive log files	DAYS_TO_KEEP_ARCHSOURCE	whole and decimal numbers (use . character), 0 to disable 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. If you are not sure, set it to 1. Ensure that enough disk space is available to store the archive logs.
5	Number of times an archive log has to be backed up by rman before being deleted	ARCHSOURCE_BACKUP_COUNT	whole numbers, 0 to disable Specify the number of times an archive log has to be backed up by RMAN before Dbvisit Standby deletes it from the primary server. If this value is set to non-zero and archivelog is never backed up by RMAN, AMM will never delete the archivelog.
6	Threshold in % of how much disk space may be used	THRESHOLD_ARCHSOURCE	percent, 0 to disable 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.
7	Threshold in % of how much FRA space may be used	FRA_THRESHOLD_ARCHSOURCE	percent, 0 to disable 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.
8	Delete archive files once threshold is reached	DELETE_ARCHSOURCE_THRESHOLD	Y or N 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.
9	Save Settings

In order to specify variables correctly, you need to make sure to understand the precedence and interaction between the variables.

2.2 Primary AMM Decision Diagram

Each AMM run on primary is done only after successful archivelog transfer and following flow is used:

2.3 Primary AMM Settings Example

Following is an example on how to set primary AMM parameters:

Following rules will apply for this setting:

AMM will perform archivelog deletion on primary after successful archivelog transfer
Criteria 1&2: AMM will delete any archivelogs exceeding the count of 100 file (oldest first) AND it will not delete any archivelog which less than exactly 1 day old
Criteria 3: AMM will delete only archivelogs which were backed up at least 1 time by RMAN
there is logical AND between criteria 1 & 2 & 3
If disk space where primary archivelogs reside is more than 85% used, dbvisit will disregard criteria 1,2 and 3 and delete archivelos in an attempt to get below the threshold
If disk FRA of primary database is more than 85% used, dbvisit will disregard criteria 1,2 and 3 and delete archivelos in an attempt to get below the threshold

2.4 Primary AMM advanced options

These options are by default not shown in dbvcontrol GUI and user must add manually parameters to the DDC file to enable these options. It is because they are only valid for specific use cases. Refer to DDC File Maintenance for details how to modify DDC parameters.

A. Multiple Standby Databases and Primary AMM

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

This value must be manually set in the DDC file, it is not possible to use dbvcontrol.

B. Multiple Archivelog Destinations with ARCHSOURCE_BACKUP_COUNT enabled on primary database and AMM

In case there are multiple archivelog destinations specified on the primary database AND ARCHSOURCE_BACKUP_COUNT is set as well, it is possible to further control behavior of AMM by setting following parameter in DDC file:

AMM_BACKUP_COUNT_FUNCTION=SUM

value SUM means that if you have log_archive_dest_1 and log_archive_dest_2 then it is enough if archivelog is backed up in one of the locations (or both locations) for the criteria ARCHSOURCE_BACKUP_COUNT to be fulfilled.

Otherwise AMM_BACKUP_COUNT_FUNCTION has default value MIN meaning that archivelog must be backed up ARCHSOURCE_BACKUP_COUNT times in log_archive_dest_1 AND in log_archive_dest_2 at the same time, otherwise the ARCHSOURCE_BACKUP_COUNT criteria isn't fulfilled.

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 Standby database db_recovery_file_dest or log_archive_dest by Dbvisit StandbyMP.

3.1 Enable AMM on standby

GUI field names and DDC variables referrence:

Number	GUI Field Name	DDC variable	Values and Explanation
2	Enable Archivelog Management on Standby	ARCHDEST_MANAGEMENT	Y or N 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).
3	Number of archive log files to keep	NUM_ARCHDEST_TO_KEEP	whole numbers, 0 to disable 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).
4	Days to keep the archive log files	DAYS_TO_KEEP_ARCHDEST	whole and decimal numbers (use . character), 0 to disable 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.
5	Threshold in % of how much disk space may be used	THRESHOLD_ARCHDEST	percent, 0 to disable 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.
6	Delete archive files once threshold is reached	DELETE_ARCHDEST_THRESHOLD	Y or N 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.

3.2 Standby AMM Decision Diagram

Each AMM run on primary is done only after successful archivelog transfer and following flow is used:

3.3 Standby AMM Settings Example

Following is an example on how to set standby AMM parameters: