tx_read_only

Description

tx_read_only specifies whether to set a transaction to read-only mode.

Privilege requirements

• Query variables

  • Global level

    sys tenants and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_GLOBAL_VARIABLE view (Oracle mode) or information_schema.GLOBAL_VARIABLES view (MySQL mode) to view the values of global system variables.

  • Session level

    sys tenants and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_SESSION_VARIABLE view (Oracle mode) or information_schema.SESSION_VARIABLES view (MySQL mode) to view the values of session system variables.

• Modify variables

  • Global level

    • sys tenants can modify the values of global system variables.

    • MySQL user tenants must have the SUPER or ALTER SYSTEM privilege to modify the values of global system variables.

    • Oracle user tenants must have the ALTER SYSTEM privilege to modify the values of global system variables.

  • Session level

    sys tenants and all user tenants can modify the values of session system variables.

Attributes

Usage notes

After you set the tx_read_only system variable:

• If the variable is set at the session level, it only affects the current user and does not affect other users.

• If the variable is set at the global level, it affects all users who connect to the database in the future.

Examples

Set a transaction to read-only mode.

• Session level

  obclient> SET tx_read_only = 1;
  

• Global level

  obclient> SET GLOBAL tx_read_only = 1;