The Prepare function creates a Restructure Plan data set and Restructure Activity data set:
The Restructure Plan data set contains information about the changes you want to make to the database. It is used for input into the Shadow Initialization and Restructure functions.
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.
In addition, the Prepare function
identifies any requested changes that are not supported for restructure processing
determines the minimum processing requirements by indicating which areas in the original database need to be processed
optionally performs an analysis of all areas that are in the source database
For the Prepare function to perform an analysis of all areas, you must have a license for the Fast Path Online Analyzer/EP product.
Shadow Initialization function
The Shadow Initialization function initializes the shadow area data sets so that they are ready for Restructure function processing.
This function receives input from the Restructure Plan data set. The Shadow Initialization function must be performed before Restructure function processing.
If secondary shadow area keywords are specified during Prepare function processing, the Shadow Initialization function initializes both the primary and secondary shadow area data sets. The secondary shadow area data set is a copy of the primary shadow area data set, which can be used for backup and recovery purposes.
The Restructure function uses the information in the Restructure Plan data set to make structural changes to the shadow area data sets while the original area data set is available to your online IMS system.
The Restructure function completes the following steps:
The Area Copy task copies all data from the original area data sets to the shadow area data sets. The required database structure changes are made during the area copy process. An IFP task is started for each area to be restructured. Multiple IFP tasks can be performed in parallel, depending on the available IMS resources.
The Change Capture task captures all DL/I updates that are made to the original area data sets.
The Change Apply task takes the captured changes and applies them to the shadow area data sets.
During post-processing, a database outage occurs. The following post-processing tasks are completed to make the restructured areas available to the online IMS system:
The Restructure function issues a /DBR command to take the restructured areas offline.
The online and primary shadow area data sets are swapped.
DBRC registration is added and other information is updated as needed.
ACB/PFX control blocks and randomizers are reloaded into your IMS system.
The Restructure function issues a /STA command to make all areas in the database available by bringing them online.
If any post-processing task fails, you can restart the task by using the Restart function.
The Restart function can be used to resume the post-processing task if a failure occurs during restructure post-processing or after early termination was requested.
The Restart function allows you to continue from a failure point without going through the entire restructure process again.
If a failure occurs during the Area Copy, Change Capture, or Change Apply tasks, execute the Shadow Initialization function, and then rerun the restructure job to resume these tasks.
The Backout function can be used to restore your database to its original state by allowing you to revert (undo) changes made by the Restructure function.
If an error occurs during restructure processing, you can undo the changes and start over (if desired).
You cannot execute the Backout function after the Restructure function completes or the DELTA step (new control blocks are moved into active libraries) for the Restructure function or Restart function has started.
The Status function can be used to generate the Restructure Activity Report on demand.
This report provides information from the Restructure Activity data set, which contains information about actions performed during the online restructure process. The report provides information for input and output area activity.