enable_lock_priority

Description

enable_lock_priority specifies whether to enable table lock priorities. When lock priorities are enabled, RENAME TABLE operations have the highest lock priority. When a RENAME TABLE operation is waiting for a table lock together with another DDL operation, a locking operation, or a DML operation, the RENAME TABLE operation is the first to obtain a table lock.

Limitations

• Query the parameter

  In the sys tenant or a user tenant, you can execute the SHOW PARAMETERS statement to query the parameter or query the GV$OB_PARAMETERS view for the parameter.

• Modify the parameter

  You can use the ALTER SYSTEM SET statement to modify the parameter in the sys tenant or a user tenant.

Attributes

Considerations

Before you use gh-ost or OceanBase Developer Center (ODC) to perform an online DDL operation, set the enable_lock_priority parameter to TRUE for the corresponding tenant and query the GV$OB_PARAMETERS view to make sure that the setting takes effect for all servers in the tenant. After the online DDL operation is completed, change the value of the parameter to FALSE to avoid impact on your DML business.

Examples

1. Enable table lock priorities.

   ALTER SYSTEM SET enable_lock_priority = TRUE;
   

2. Query the value of the enable_lock_priority parameter.

   SHOW PARAMETERS LIKE 'enable_lock_priority';
   

   The query result is as follows:

   +-------+----------+----------------+----------+----------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+---------+--------+---------+-------------------+---------------+-----------+
   | zone  | svr_type | svr_ip         | svr_port | name                 | data_type | value | info                                                                                                                              | section | scope  | source  | edit_level        | default_value | isdefault |
   +-------+----------+----------------+----------+----------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+---------+--------+---------+-------------------+---------------+-----------+
   | zone1 | observer | xxx.xx.xxx.001 |     2882 | enable_lock_priority | NULL      | True  | specifies whether to enable lock priority, which, when activated, gives certain DDL operations the highest table lock precedence. | TRANS   | TENANT | DEFAULT | DYNAMIC_EFFECTIVE | False         |         0 |
   | zone2 | observer | xxx.xx.xxx.002 |     2882 | enable_lock_priority | NULL      | True  | specifies whether to enable lock priority, which, when activated, gives certain DDL operations the highest table lock precedence. | TRANS   | TENANT | DEFAULT | DYNAMIC_EFFECTIVE | False         |         0 |
   | zone3 | observer | xxx.xx.xxx.003 |     2882 | enable_lock_priority | NULL      | True  | specifies whether to enable lock priority, which, when activated, gives certain DDL operations the highest table lock precedence. | TRANS   | TENANT | DEFAULT | DYNAMIC_EFFECTIVE | False         |         0 |
   +-------+----------+----------------+----------+----------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+---------+--------+---------+-------------------+---------------+-----------+
   1 row in set
   

3. Disable table lock priorities.

   ALTER SYSTEM SET enable_lock_priority = FALSE;