Two-Phase Commit Support with RRS › RRS Support for Batch Applications › Batch RRS Transaction Boundaries and Application Design Considerations

Batch RRS Transaction Boundaries and Application Design Considerations

Batch applications that use RRS as a coordinator have to be carefully designed. The usage of RRS implies the following rules:

• The application verbs that mark a transaction boundary are the RRS verbs: Commit_UR or Backout_UR.
• Prior to issuing a Commit_UR, all database sessions whose transaction is under the control of RRS must be completed. This can be accomplished by performing the following tasks:
  • Issuing a FINISH TASK DML command
  • Explicitly finishing all active database sessions by issuing a FINISH or COMMIT RELEASE DML command for each one

  Note: A FINISH TASK must be issued if a BIND TASK was issued.

  Finishing a database session does not terminate its associated transaction when it is under the control of RRS; instead, the database session is closed and currency locks are released, but the transaction remains active and update locks are maintained until the RRS UR is committed or backed out.

  It is possible to serially create and finish database sessions within a single RRS UR; however, unless transaction sharing is in effect, a deadlock may occur if a later session attempts to access a record that was updated by a previous session.

• When a ROLLBACK [TASK] DML command is issued, it results in the back out of the entire RRS UR, even if the application subsequently issues a Commit_UR request. At the time the ROLLBACK command is issued, the changes made to the CA IDMS database are backed out and the associated locks are released. However, the RRS UR is not backed out until an RRS commit or backout operation is initiated. If necessary, CA IDMS will initiate a BACKOUT operation during the first phase of commit processing to cause the RRS UR to be backed out.
• When an application program ends (normally or abnormally), the associated RRS context is terminated by the operating system. RRS default actions are to commit on normal context termination and backout on abnormal context termination.