Prepare function overview

• The Restructure Plan data set contains information that is needed to restructure a DEDB online. It is used for input into the Shadow Initialization function, Restructure function, and the Restart function (if needed).

• The Restructure Activity data set contains information about the actions performed during the online restructure process. It is used for input into the Restart, Backout, and Status functions and output from the Prepare, Shadow Initialization, Restructure, and Restart functions.

Fast Path Online Restructure/EP uses the PREPARE command to determine a list of specific ACB members and, if applicable, PFXLIB members that will be affected by restructuring the specified DEDB. The RESTRUCTURE post-processing phase then copies those selected members from the staging library into the active production library. This information is written into the PLAN file.

The Prepare function must be performed before the actual restructure process. The Prepare function can be performed anytime (days or even weeks ahead of the actual restructure process). It can also be performed several times before the actual restructure process is initiated, allowing you to evaluate different design alternatives.

Before the Prepare function can be executed, you must first create the appropriate control blocks and load modules that are required for the new restructured database design. The Prepare function analyzes the changes between the existing (old) database design and the proposed (new) design. Included in these changes are any changes to the definitions of PFX indexes and IBM native indexes.You can review the output to evaluate the proposed design and to plan the actual restructure of the database.

The Prepare function executes an online (IFP region) utility program. The IFP utility program compares the control blocks and load modules that define the existing (old) database with the control blocks and load modules that define the restructured (new) database.

The output from the Prepare function is saved as a Restructure Plan data set that is used as input into the Shadow Initialization function, Restructure function, and Restart function (if needed). The information is saved in a format that cannot be modified. As a result, no additional design changes can be made between the execution of the Prepare function and the Restructure function. If additional changes are made, the Prepare function must be executed again.

Preparing a DEDB for an online restructure by using the Prepare function yields less I/O, processing time, and downtime during the restructure process.

This section contains the following topics:

• Identifying changes
• Determining minimum processing requirements