|
|
|
Record Definition Language (RDL) provides you with a formal means of describing characteristics of the data comprising a file that is compressed (and expanded) by the CA Compress system, using a user-generated FDT. The more you know about the data, the more detailed and precise the RDL specifications can be.
RDL is used only for user-defined FDTs. Because the execution of any RDL specification must be serialized, user-defined FDTs impose a significant I/O penalty where multiple I/Os are issued concurrently, as in busy CICS systems. Super Express, Standard Tables, and Hardware compression do not require this serialization, so we strongly recommend them where they give acceptable compression.
Even for user-defined FDTs, CA Compress assumes default record definitions (described at the end of this chapter) if you choose not to code RDL specifications. CA Compress effectiveness in achieving impressive compression ratios using default record definitions (and corresponding low processing overhead) is considerable. In the absence of other considerations (for example, the need to exempt specific nonkey fields from compression, for which user-coded RDL specifications are necessary) we recommend that the default definitions assumed by the CA Compress system be used in the first attempts to compress any file. Then, if performance is satisfactory, no more user coding is necessary.
This chapter describes how to create your own RDL, if you need to do it.
This section contains the following topics:
Performance Considerations When Using RDL
General Restrictions on RDL Use
Guide to Correct RDL Specifications
Determining the Best Compression
| Copyright © 2012 CA. All rights reserved. |
|