Physical Backup and Restoration ​

PITR ​

Background ​

When the database breaks down or needs to be rolled back to a previous state, the point-in-time recovery (PITR) function of openGauss can be used to restore the database to any time point after the backup and archived data is generated.

Prerequisites ​

• Full data files have been physically backed up.
• WAL files have been archived.

PITR Process ​

1. Replace the target database directory with the physical backup files.
2. Delete all files in the database directory pg_xlog/.
3. Copy the archived WAL files to the pg_xlog file. (You can configure restore_command in the recovery.conf file to skip this step.)
4. Create the recovery.conf file in the database directory and specify the database restoration degree.
5. Start the database.
6. Connect to the database and check whether the database is restored to the expected state.
7. If the expected state is reached, run the pg_xlog_replay_resume() command to enable the primary node to provide services externally.

Configuring the recovery.conf File ​

Archive Restoration Configuration

• restore_command = string

The shell command is used to obtain the archived WAL files among the WAL file series. Any %f in the string is replaced by the name of the file retrieved from the archived files. Any %p is replaced by the path name of the replication destination on the server. Any %r is replaced by the name of the file containing the latest valid restart point.

Example:

restore_command = 'cp /mnt/server/archivedir/%f %p'

• archive_cleanup_command = string

This parameter declares a shell command that is executed each time the system is restarted. archive_cleanup_command provides a mechanism for deleting unnecessary archived WAL files from the standby database. Any %r is replaced by the name of the file containing the latest valid restart point. The file is the earliest file that must be kept to allow restoration to be restartable, so that all files earlier than the value of %r can be safely removed.

Example:

archive_cleanup_command = 'pg_archivecleanup /mnt/server/archivedir %r'

If multiple standby servers need to be restored from the same archive path, ensure that the WAL files are not deleted from any standby server before the restoration.

• recovery_end_command = string

This parameter is optional and is used to declare a shell command that is executed only when the restoration is complete. recovery_end_command provides a cleanup mechanism for future replication and restoration.

Restoration Object Configuration

• recovery_target_name = string

This parameter declares that the name is restored to a restoration point created by using pg_create_restore_point().

Example:

recovery_target_name = 'restore_point_1'

• recovery_target_time = timestamp

This parameter declares that the name is restored to a specified timestamp.

Example:

recovery_target_time = '2020-01-01 12:00:00'

• recovery_target_xid = string

This parameter declares that the name is restored to a transaction ID.

Example:

recovery_target_xid = '3000'

• recovery_target_lsn = string

This parameter declares that the name is restored to the LSN specified by logs.

Example:

recovery_target_lsn = '0/0FFFFFF'

• recovery_target_inclusive = boolean

This parameter declares whether to stop the restoration after the restoration target is specified (true) or before the restoration target is specified (false). This declaration supports only the restoration targets recovery_target_time, recovery_target_xid, and recovery_target_lsn.

Example:

recovery_target_inclusive = true