Parameters related to physical restore|V4.1.0| docs|Distributed Database

Parameters related to physical restore

Last Updated：2023-07-28 02:55:42 Updated

This topic describes the parameters in restore statements.

Parameters in the RESTORE statements

Statements

Restore to a specified timestamp

obclient [(none)]>ALTER SYSTEM RESTORE dest_tenant_name FROM uri UNTIL TIME=timestamp WITH restore_option [DESCRIPTION description];

Restore to a specified SCN

obclient [(none)]>ALTER SYSTEM RESTORE dest_tenant_name FROM uri UNTIL SCN=scn WITH restore_option [DESCRIPTION description];

Restore to the latest checkpoint

obclient [(none)]> ALTER SYSTEM RESTORE dest_tenant_name FROM uri WITH restore_option [DESCRIPTION description];

Parameters

Parameter	Description
dest_tenant_name	The name of the destination tenant to which the data is to be restored.
uri	The data backup path `backup_data_dest` and log archive path `log_archive_dest` specified during restore. The value must contain at least one data backup path and one log archive path that are separated with a comma (`,`).
timestamp	The timestamp to which data is restored. Join the parameter name and value with an equal sign (`=`). The timestamp must be in the `YYYY-MM-DD HH24:MI:SS.FF` format, accurate to nanoseconds.
scn	The SCN to which data is restored. Join the parameter name and value with an equal sign (`=`).
restore_option	The restore options, including `pool_list`, `locality`, `primary_zone`, and `kms_encrypt`. Separate the options with ampersands (`&`). `pool_list`: Required. The resource pool of the tenant. Multiple resource pools must be separated with commas (,). `locality`: Optional. The locality of replicas of the new tenant, which must match the zone information of `pool_list` of the cluster where the new tenant is located. By default, if this parameter is not specified, a full-featured replica is set for each zone in `zone_list` of the resource pool. Example: `locality='F@z1,F@z2,F@z3'` `primary_zone`: Optional. The preferred position of the leader of the new tenant, which must match the settings of `pool_list` and `locality`. In other words, it must match the zone information and meet the constraint that `primary_region` must have at least two Paxos members. If this parameter is not specified, the system randomly distributes leaders in the zones specified by `zone_list` of `locality`. Example: `primary_zone='z1'` `kms_encrypt`: Optional. This option specifies whether encryption information is required. If the value is `true`, the value of `kms_encrypt_info` specified in restore preparations is required. Default value: `false`.
description	Optional. The description.

Constraint for specifying the timestamp and SCN

The timestamp and SCN must be greater than or equal to the minimum restore SCN indicated by MIN_RESTORE_SCN in the data backup view CDB_OB_BACKUP_SET_FILES, and smaller than or equal to the maximum archive SCN indicated by CHECKPOINT_SCN in the log archive view CDB_OB_ARCHIVE_LOG. Log archiving may be interrupted. Therefore, you must consider inconsecutive ranges of logs when you specify the restore SCN. The restorable window may be discontinuous.

Assume that:

Two log archive rounds were initiated, with the round_id values of 1 and 2.
Three data backup jobs were initiated, which produced three valid data backup sets: full_backup_set_1, full_backup_set_2, and inc_backup_set_3.

The following figure shows the restorable window for physical restore. The right boundary of a data backup set is specified by MIN_RESTORE_SCN. For example, MIN_RESTORE_SCN of full_backup_set_1 corresponds to scn 300 in the figure. The right boundary of a log archive is specified by CHECKPOINT_SCN. For example, CHECKPOINT_SCN of round 1 corresponds to scn 500 in the figure.

Restorable window

Log archiving may be interrupted. Therefore, you must consider the inconsecutive time ranges when you calculate the restorable window. As a result, the restorable window is discontinuous. In the figure, the restorable window is [scn 300, scn 500] u [scn 900, scn 1500].

Parameters in the restore performance tuning statement

Statement

obclient [(none)]> ALTER SYSTEM SET ha_high_thread_score =10 TENANT = mysql;

Parameter

Parameter	Description
ha_high_thread_score	Specifies the weight of threads for the restore job queue.

Parameters in the RECOVER statements

Statements

Replay logs to the specified timestamp.

ALTER SYSTEM RECOVER STANDBY [TENANT tenant_name] UNTIL TIME='timestamp';

Replay logs to the specified SCN.

ALTER SYSTEM RECOVER STANDBY [TENANT tenant_name] UNTIL SCN=scn;

Continuously replay logs from the archive source without specifying the end point.
```
ALTER SYSTEM RECOVER STANDBY [TENANT tenant_name] UNTIL UNLIMITED;
```

Cancel a log replay

ALTER SYSTEM RECOVER STANDBY TENANT tenant_name CANCEL;

Parameters

Parameter	Description
tenant_name	The tenant name.
timestamp	The timestamp to which data is restored. Join the parameter name and value with an equal sign (`=`). The timestamp must be in the `YYYY-MM-DD HH24:MI:SS.FF` format, accurate to nanoseconds.
scn	The SCN to which data is restored. Join the parameter name and value with an equal sign (`=`).
UNLIMITED	Specifies to continuously replay logs from the archive source without specifying the end point.

Parameters in the ACTIVATE statement

Statement

obclient [(none)]> ALTER SYSTEM ACTIVATE STANDBY TENANT tenant_name;

Parameters

Parameter	Description
tenant_name	The name of the standby tenant that is restored. You can use this statement to change the role of only one tenant at a time.