How IMS protects data integrity for CICS online programs

IMS can protect the data integrity for CICS® online programs.

IMS protects the integrity of the database for programs that share data by:

• Preventing other application programs with update capability from accessing any segments in the database record your program is processing, until your program finishes with that record and moves to a new database record in the same database.
• Preventing other application programs from accessing segments that your program deletes, replaces, or inserts, until your program reaches a sync point. When your program reaches a sync point, the changes your program has made to the database become permanent, and the changed data becomes available to other application programs.

  Exception: If PROCOPT=GO has been defined during PSBGEN for your program, your program can access segments that have been updated but not committed by another program.

• Backing out database updates made by an application program that terminates abnormally.

You may also want to protect the data your program accesses by retaining segments for the sole use of your program until your program reaches a sync point—even if you do not update the segments. (Ordinarily, if you do not update the segments, IMS releases them when your program moves to a new database record.) You can use the Q command code to reserve segments for the exclusive use of your program. You should use this option only when necessary because it makes data unavailable to other programs and can have an impact on performance.