Analyzing a DEDB offline with FPB

You can analyze a DEDB by using the DEDB Pointer Checker utility of FPB.

The DEDB was introduced as part of the Fast Path feature of IMS. It is the preferred access method for databases in high performance, random processing environments. The use of DEDBs, even in MPPs, can significantly increase transaction throughput and reduce response time. Besides having the potential for the most random performance, poorly tuned DEDBs have the potential to be inefficient because excessive physical I/O can occur when accessing the database. Also, integrity verification and space/performance management utilities for DEDBs were not provided with IMS.

FPB DEDB Pointer Checker provides a fast, efficient mechanism for verifying the integrity of all IMS pointer values, free space element chains, VSAM control fields, and space utilization in IMS DEDBs. DEDB Pointer Checker provides the comprehensive analysis information required to effectively manage the space utilization, performance characteristics, and physical attributes of IMS DEDBs. DEDB Pointer Checker uses as input either an image copy data set or the VSAM cluster. DEDB Pointer Checker can be an aid for database administrators and technical support personnel in database management, maintenance, and performance tuning.

The DEDB Pointer Checker product requires no source code modifications to any user or IMS module.

The three Pointer Checkers of IMS HP Fast Path Utilities

There are three distinct pointer checker products. Therefore, before getting started, it is important to read this topic in order to avoid confusion later on.

This topic describes the relationship among the following three Pointer Checkers:

  • Analyze function of FPA
  • DEDB Pointer Checker of FPB
  • Online Pointer Checker of FPO

The Analyze function of FPA and DEDB Pointer Checker of FPB run in the offline environment and Online Pointer Checker of FPO runs in the online environment.

The Analyze function of FPA is part of the IMS HP Fast Path Utilities package. It has the function similar to that of DEDB Pointer Checker, which runs while the database area is offline. FPA verifies the integrity of all IMS pointer values and verifies the integrity of the pointer segments in secondary index databases. It also produces complete analysis reports in one step, whereas DEDB Pointer Checker runs the same functions in multiple steps.

DEDB Pointer Checker of FPB is also part of the IMS HP Fast Path Utilities package. It uses program FABADA1 to collect pointer verification data. This program must be run while the database area is offline. The collected data can then be passed to the pointer integrity checking programs and various report generating programs in this package.

Online Pointer Checker of FPO is also part of the IMS HP Fast Path Utilities package. It runs as a Fast Path utility to verify the integrity of all IMS pointer values and produce complete analysis reports in one step while the database area is online. However, you can use OPC to run a fast scan of database integrity and collect pointer verification data from an online DEDB area, then pass it to DEDB Pointer Checker of FPB to check cross-reference of pointers and produce complete analysis reports. This type reduces the online run time but must be run in multiple steps.