tx_read_only

Description

The tx_read_only variable specifies whether a transaction is read-only.

Privilege requirements

• Query variables

  • Global level

    The sys tenant and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_GLOBAL_VARIABLE view (in Oracle-compatible mode) or the information_schema.GLOBAL_VARIABLES view (in MySQL-compatible mode) to query the value of a global system variable.

  • Session level

    The sys tenant and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_SESSION_VARIABLE view (in Oracle-compatible mode) or the information_schema.SESSION_VARIABLES view (in MySQL-compatible mode) to query the value of a session variable.

• Modify variables

  • Global level

    • The sys tenant can directly modify the value of a global system variable.

    • MySQL-compatible tenants must have the SUPER or ALTER SYSTEM privilege to modify the value of a global system variable.

    • Oracle-compatible tenants must have the ALTER SYSTEM privilege to modify the value of a global system variable.

  • Session variables

    The sys tenant and all user tenants can directly modify the value of a session system variable in their respective tenant.

Attributes

Considerations

After you set the tx_read_only variable, the setting takes effect as follows:

• If the setting takes effect at the session level, it affects only the current user and does not affect other users.

• If the setting takes effect at the global level, it affects all users who establish new connections.

Examples

Set a transaction to be read-only.

• Session level

  obclient> SET tx_read_only = 1;
  

• Global level

  obclient> SET GLOBAL tx_read_only = 1;