tx_read_only

Description

tx_read_only specifies whether to enable the transaction read/write mode for transactions, that is, whether to set the transaction as read-only.

Privilege requirements

• Query variables

  • Global level

    In both Oracle and MySQL modes, you 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 from the sys tenant and all user tenants.

  • Session level

    The sys tenant and all user tenants can view the values of session system variables by using the SHOW VARIABLES statement, or by querying the views SYS.TENANT_VIRTUAL_SESSION_VARIABLE (Oracle mode) or information_schema.SESSION_VARIABLES (MySQL mode).

• Modify variables

  • Global level

    • The sys tenant can directly modify the values of global system variables.

    • MySQL users of user tenants have the SUPER or ALTER SYSTEM privilege, which allows them to modify the values of global system variables.

    • For V4.x, starting from V4.2.0, an Oracle user tenant must have the ALTER SYSTEM privilege to modify the values of global system variables.

  • Session level

    Both the sys tenant and user tenants can directly modify the values of session system variables in their own tenants.

Attributes

User Guide

After you set the tx_read_only system variable:

• If session-level, the setting affects only the current user and does not affect other users.

• If this setting takes effect at the global level, it will impact all users for all subsequent new connections.

Examples

Set the transaction to read-only.

• Session level

  obclient> SET tx_read_only = 1;
  

• Global level

  obclient> SET GLOBAL tx_read_only = 1;