Database pointer check (HASH Check)

The Image Copy function can check the accuracy of database pointers while it creates image copies. By enabling the Hash Check option, you need only to take image copies instead of running pointer check utilities to verify the pointers of databases. You can reduce the number of jobs for verifying the pointers of image copies taken.

HASH Check is supported for DL/I databases, High Availability Large Databases (HALDB), and Data Entry Databases (DEDB). HASH Check is provided by the following programs:

HD Pointer Checker utility of IMS HP Pointer Checker: When IMS HP Pointer Checker is used regularly, it helps ensure that your database pointers are error free, alerting you when it is time to perform a database reorganization. To help programmers analyze corrupted databases, IMS HP Pointer Checker provides important information that helps to reduce the time spent handling diagnostics and repairs. These reports reveal errors and their locations within the database, facilitating system tuning and optimization.
If you enable the HASH Check option of the HD Pointer Checker utility within an image copy job for an IMS full-function database, HALDB database, or both, you can check the accuracy of the image copy while image copy processes are running.
DEDB Pointer Checker utility of IMS HP Fast Path Utilities: IMS Fast Path Solution Pack is composed of multiple tools and utilities. By using these tools and utilities, you can easily and quickly develop a standard, single driver for unloading, reloading, reorganizing, analyzing, and extracting multiple Data Entry Database (DEDB) areas.
If you enable the HASH Check option of the DEDB Pointer Checker utility within an image copy job for a DEDB, you can check the accuracy of the image copy while image copy processes are running.

HD Pointer Checker HASH Check option

IMS HP Image Copy supports two methods for invoking the HD Pointer Checker HASH Check option:

Single-step HASH Check: Submit an image copy job to run Hash Check job in single step.
Multiple-step HASH Check: Run a DBD analysis program step before the Image Copy step, and a HASH evaluation program step after the image copy step.

Single-step HASH Check is recommended if you want to create and run the JCL with simple steps. Multiple-step HASH Check is recommended, however, if you want to shorten the time needed to get the image copy. With multiple-step HASH Check, HD Pointer Checker HASH Check is done after creating image copies. If, for example, there are many data sets of which you want to make image copies, run the image copy jobs separately, but run the HASH evaluation program only once.

You can request this feature by specifying the HDPC keyword in the ICEIN control statement.

You can also start the Space Monitor utility of IMS HP Pointer Checker during the IMS HP Image Copy job. The Space Monitor utility checks the database data sets and reports on space utilization. You can request this feature by specifying the SPMN keyword in the ICEIN control statement.

DEDB Pointer Checker HASH Check option

The DEDB Pointer Checker HASH Check option can be used to verify the pointers of DEDB areas.

You can request this feature by using the DEDBPC keyword in the ICEIN control statement.

Types of errors detected by HASH Check option

During HASH Check, the HD Pointer Checker or the DEDB Pointer Checker detects the following two types of errors:

Unidentified error: Pointer Checker reports an error as an unidentified error when the cause of the error could be considered as the target database being updated. An unidentified error might not be a pointer error and it might be resolved when the database becomes stable. You can run the stand-alone Pointer Checker to identify the cause of an unidentified error.
Severe error: Pointer Checker reports an error as a severe error when the cause of the error is determined as the target database being corrupted and that the database is in need of repair.

These errors are reported in the Image Copy Process Summary report.