Overview of batch IMS Database Repair Facility for VSAM

An important feature of the batch version of IMS Database Repair Facility is that you can use it to modify both IMS and non-IMS VSAM data sets. You might already be familiar with the MVS™ SPZAP (Superzap) program. The batch version of IMS Database Repair Facility operates in a similar manner.

You can specify the data to change by supplying the following information to IMS Database Repair Facility:

Key (KSDS only)
Relative byte address (RBA) (KSDS and ESDS)
Relative-record number (RRDS only)
Control interval (all types)

When SYSIN control statements are used as part of a batch job, messages are sent to SYSPRINT. When the system console is used to enter control statements, messages are sent to the console. You can receive reports in the SYSPRINT data set for verification whether you are using a batch job or the system console.

Functions

The batch version of IMS Database Repair Facility supports the following three functions:

Verify function

Compares data before changing the data.

The Verify function compares the data at a specific location in a VSAM data set to data that you supply.

Recommendation: A Verify operation should always be done before a Replace operation. If, during a Verify operation, the batch IMS Database Repair Facility finds that the two data fields it is comparing are not the same, the Replace operation is canceled. This feature prevents making accidental changes to valid data. When you use the batch IMS Database Repair Facility, data is compared to verify that it is the same. If data is not the same, the data that is in the VSAM data set is either printed in a report format or is displayed on your terminal screen.

Replace function

Changes data.

The Replace function changes the data at a specific location in a VSAM data set with data that you supply.

Recommendation: To eliminate the possibility of changing good data, always perform a Verify operation before a Replace operation. If data does not match during a Verify operation, the Replace is canceled. If data does not match during a Verify operation, the program ignores following Replace requests for that data. A Replace does not occur until the next Key, RBA, record number, or control interval statement is found.

Dump function

Prints the VSAM record or control interval (CIs).

The Dump function prints a dump for a part of a VSAM data set to the SYSPRINT output report.

A Dump is executed for the record or CI that is specified immediately before the Dump command. When a Dump is performed after a Replace, the Dump reflects the changes that are made by the Replace. If a Verify operation fails, the succeeding Dump operation is ignored.

You can use Verify, Replace, and Dump functions on all types of VSAM data sets:

KSDS (key-sequenced data sets, including extended format KSDS and extended addressable KSDS)
ESDS (entry-sequenced data sets, including extended format ESDS)
LDS (linear data sets, including extended format LDS and extended addressable LDS)
RRDS (relative-record data sets)

Typical uses

The batch version of IMS Database Repair Facility is used as follows:

To perform Verify, Replace, and Dump operations in all types of VSAM data sets
To access either individual records or the complete control interval
To verify up to 36 bytes per Verify statement
To replace up to 36 bytes per Replace statement
To perform multiple Verify operations
To perform multiple Replace operations
To retrieve any number of records or control intervals with one run
To satisfy data set security with a password control statement

Program structure

The batch version of IMS Database Repair Facility operates as a batch program in the MVS region. The utility is independent of IMS releases. It requires current VSAM support generated in the System Control Program, and runs in the current problem program state.

Restrictions

When you access a compressed data set with the batch version of IMS Database Repair Facility, the following restrictions apply:

You cannot perform any IMS Database Repair Facility function by using the relative byte address of the control interval on the CNV control statement.
You cannot perform the Replace function by using the relative byte address of the VSAM record on the RBA control statement.

However, you can perform all batch IMS Database Repair Facility functions, Verify, Replace, and Dump, using the fully qualified key of the VSAM record on the KEY control statement.