ls_gc_delay_time

Description

The ls_gc_delay_time parameter specifies the duration for which the log streams of a tenant are delayed before being deleted.

OceanBase Database V4.2.0 introduced a load balancing module based on log splitting and merging. This allows the database to scale out and scale in. When you scale in OceanBase Database, logs that meet the garbage collection (GC) conditions are removed, and the corresponding log storage is cleared.

In addition, OceanBase Database has implemented physical standby databases based on the network starting with V4.2.0. When the source primary or standby tenant has not enabled log archiving and the database undergoes a scaling down operation, the log stream will be quickly cleared. This can lead to overall log synchronization being held up due to the recycling of logs. Therefore, you need to configure the delay time for log stream deletion for the source primary or standby tenant using this parameter.

Privilege requirements

• Query the parameter

  The sys tenant and all user tenants can query this parameter by executing the SHOW PARAMETERS statement or querying the GV$OB_PARAMETERS view.

• Modify the parameter

  You can use the sys tenant or a user tenant to modify the parameters.

Attributes

Considerations

• In physical standby scenarios:

  • If logs are not archived for the primary or standby tenants on the source, and the default value of the ls_gc_delay_time parameter is 3600s (1 hour), the log delayed deletion mechanism is activated, with a delay period of 1 hour for the log streams.

  • If log archiving is enabled for the primary or standby tenant of the source database, the log stream data integrity is guaranteed by log archiving. Therefore, the garbage collection (GC) of the log streams is not affected by this parameter. In this scenario, the log delay deletion mechanism does not take effect, regardless of the value of the ls_gc_delay_time parameter.

• For a scenario where a tenant is deleted, the log stream delayed deletion mechanism will not take effect regardless of the value of the ls_gc_delay_time parameter.

  Note

  The only data that remains after deletion is the log stream entities. Whether the log files of the log stream can be retained depends on the available disk space for the current tenant. If the available disk space is insufficient, log recovery will still be triggered.

Examples

• Specify the delay period before a tenant log stream is automatically deleted in the sys tenant.

  obclient> ALTER SYSTEM SET ls_gc_delay_time='7200s' TENANT = 'mysql_tenant';
  

• You can set the delayed deletion time of the log stream for the current user tenant.

  obclient> ALTER SYSTEM SET ls_gc_delay_time='7200s';