Extended Compression Architecture

XCA has these components:

• BCSS—the XCA control facility that directs the other components
• Set of compression techniques—Dynamic Adaptive, Arithmetic Adaptive, Extended Character, Static Huffman, Repeating Character, Hardware, and Custom Dictionary for Hardware

• REGISET—the collection of registration data sets defined during the installation process

  Each registration data set in the REGISET contains the following information for DATA ACCELERATOR Compression:

  • Compressed data sets and compression and expansion specifications
  • Programs whose data set output operations will not be compressed or whose data set input operations will not be expanded

With DATA ACCELERATOR Compression, XCA provides the following benefits:

• The BCSS provides commonly used services for BMC products that use XCA. The BCSS also allocates compression routines in the local address space (local compression) or in a compression address space (CAS compression). Many jobs can use a single CAS; however, the BCSS creates and supports more compression address spaces when needed. The BCSS also maintains the registration data sets.
• To reduce the burden on your system, multiple BMC products can share XCA.
• XCA provides resource management for itself and the BMC products that use XCA. When a product no longer needs a resource, XCA frees the resource.
• XCA reduces local and CAS virtual storage requirements.
  • If you choose local compression, all compression routines and work areas are located above the 16-MB line at the top of the extended private area.
  • If you choose CAS compression, the compression routines and work areas are isolated in their own address space.
• You can continue normal DATA ACCELERATOR Compression operations when applying changes or enhancements to the compression routines. The new techniques can expand data compressed with previously selected techniques.

The following figures illustrate the relationships between DATA ACCELERATOR Compression and the XCA components while using local and CAS compression.