SHISAM IMS symbolic checkpoint call

SHISAM is also useful if you need an application program that accesses z/OS® data sets to use the IMS symbolic checkpoint call.

The IMS symbolic checkpoint call makes restart easier than the z/OS basic checkpoint call. If the z/OS data set the application program is using is converted to a SHISAM database data set, the symbolic checkpoint call can be used. This allows application programs to take checkpoints during processing and then restart their programs from a checkpoint. The primary advantage of this is that, if the system fails, application programs can recover from a checkpoint rather than lose all processing that has been done. One exception applies to this: An application program for initially loading a database that uses VSAM as the operating system access method cannot be restarted from a checkpoint. Application programs using GSAM databases can also issue symbolic checkpoint calls. Application programs using SHSAM databases cannot.

Before deciding to use SHISAM, you should read the next topic on GSAM databases. GSAM has many of the same functions as SHISAM. Unlike SHISAM, however, GSAM files cannot be accessed from a message processing region.

SHISAM databases can use field-level sensitivity and Data Capture exit routines, but they cannot use any of the following options: