15.00 - ROLLBACK SESSION...PERFORMANCE GROUP - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
15.00
Content Type
Configuration
Publication ID
B035-1102-015K
Language
English (United States)
Last Update
2018-09-25

ROLLBACK SESSION...PERFORMANCE GROUP

Purpose  

The ROLLBACK SESSION... PERFORMANCE GROUP command sets or displays the Performance Group of rollbacks for a specified session.

Syntax  

 

Syntax element...

Specifies the...

host_id

session _id

identifiers for the host and session whose Performance Group you want to see or set.

You must specify both these identifiers in the order mentioned: host_id followed by a comma and session _id.

The session _id maximum is 4294967296.

The session _id must be in the rollback list, that is, at least one of the tables in the LIST ROLLBACK TABLES list must be from the session specified. For other rules, see “Usage Notes” on page 845.

Perf_Group_Name

name of a Performance Group whose priority level you want to apply to rollback operations in the specified session. (Optional)

The Teradata Database system will execute rollbacks in the specified session at the priority level associated with this Performance Group.

You can specify one of the pre-defined Performance Groups: L (low), M (medium), H (high) or R (rush). The default priority is R. Any Performance Group other than these has to be explicitly defined for usage.

If you do not specify a Perf_Group_Name, then the current Performance Group of the session is displayed.

For details on Performance Groups, see Chapter 18: “Priority Scheduler (schmon) (SLES 10 only).”

Usage Notes

Rollback processing runs at the priority defined for the session, that is, the priority associated with the Performance Group for the session. If no priority is specified, rollback runs at R priority by default.

The ROLLBACK SESSION... PERFORMANCE GROUP command allows you to change the priority. By reducing the priority of less important rollbacks, you can increase the Teradata Database system resource availability for other processes in the Teradata Database system.

The ROLLBACK SESSION... PERFORMANCE GROUP command affects the Performance Group and priority only for the rollback process, not for the user session.

If the DBS Control General field RollbackPriority is set to TRUE, the rollback process runs with the priority with which the recent request of the transaction was submitted. Here the ROLLBACK SESSION... PERFORMANCE GROUP command can override the DBS Control Rollback Priority field setting and change the priority of the rollback at any point of time.

The following usage rules apply to the ROLLBACK SESSION... PERFORMANCE GROUP command:

  • The host-id and the session-id specified with the ROLLBACK SESSION...PERFORMANCE GROUP command must be in the rollback tables list generated by the LIST ROLLBACK TABLES command from rcvmanager. This indicates that rollback is in progress in that session. You either can display or change the Performance Group.
  • If you specify a host-id or a session-id that does not exist in the rollback list, rcvmanager displays a message, and the command is ignored.

    Example 1: Valid Command

    The Performance Group H specified in the following command takes effect for the named host-id and session-id.

    > ROLLBACK SESSION 52, 1664 PERFORMANCE GROUP H;
    ROLLBACK SESSION PERFORMANCE GROUP command completed successfully.

    Example 2: Non-valid Command

    The following command does not take effect because the host-id and session-id are not in the rollback list and are not valid.

    > ROLLBACK SESSION 1, 1005 PERFORMANCE GROUP;
    No rollback in progress in host 1, session 1005.
    Enter command, "QUIT;" or "HELP;" 
  • If you do not specify a Performance Group with the ROLLBACK SESSION... PERFORMANCE GROUP command, then the output displays the current Performance Group setting for the specified host-id and session-id.
  • In this example, no new Performance Group name is specified. rcvmanager displays the current Performance Group for the session.

    > ROLLBACK SESSION 52, 1664 PERFORMANCE GROUP;
    Current rollback Performance Group for host 52 session 1664 is M.
  • When you execute the ROLLBACK SESSION... PERFORMANCE GROUP command, an event is logged in the Teradata Database system, even if the specified Performance Group is the same as the current Performance Group.
  • If you specify an invalid Performance Group name, no event is logged.

    The following example displays the event log entry after successful execution of the rcvmanager command.

    > ROLLBACK SESSION 52, 1664 PERFORMANCE GROUP H;
    ROLLBACK SESSION PERFORMANCE GROUP command completed successfully.
     
    02/01/31 15:34:28 Rollback Performance Group for 52, 1664 changed to H; 
    it was M.
  • When you specify a user-defined Performance Group name, the equivalent priority for that Performance Group is obtained to change the priority of the rollback for the specified host-id and session-id.
  • If the specified Performance Group is not valid, rcvmanager reports a message, and the command is ignored.

    In this example, the Performance Group name is not valid.
    > ROLLBACK SESSION 52, 1664 Performance Group InvPrfGrp;
     
    The specified Performance Group name is invalid.
    Enter command, "QUIT;" or "HELP;" :