Concepts and Facilities › Data Compression Algorithms › Scheduled and Batch Implementations

Scheduled and Batch Implementations

CA Compress provides two basic modes of implementing compression of VSAM data sets:

• Scheduled implementation immediately registers the data set and selected algorithm in the CA Compress Control File. The next time the data set is accessed by any application program, data compression support begins. Scheduled implementation is a method of immediately starting to realize the benefits of compression. As existing records are updated or new records added to the data set, they are written in compressed form. You get the benefits of reduced DASD requirements without having to take the data set offline to unload and reload it. Scheduled implementation can be configured to begin compression the next time the data set is opened or the next time CA Compress senses the data set is being loaded.
• Batch compression achieves all of the compression benefits at once. Some advantages are associated with taking a data set out of service and compressing all of the records in one cycle. CA Compress does all or most of the work required to prepare JCL and control information for Batch implementation. It automatically builds all the necessary steps—Unload, Delete, Registration, Redefine and Reload. The JCL generated can be edited, saved, or immediately submitted for execution.

For physical sequential transparent data sets, there is never key movement, and there should never be compressed and uncompressed records in the same data set. For these reasons, there is no explicit support for scheduled implementation for physical sequential transparent data sets, but future or immediate implementation is supported by means of the effective date, which you can supply through the IUI or the Control File Utility.