Changing compression techniques for a full-function database

A compression technique change is comparable to a database change. As with most database changes, converting the data requires a reorganization.

To change compression techniques for a full-function database, you must change the technique in the current registration record. If a record does not exist, you must add the record to the DPICDS. When you register your databases, registration records are created in the DPICDS to specify compression, statistics, and message options other than the Data Packer defaults.

It is important when and how you change the DPICDS. This section describes the recommended steps for two different scenarios that can be used to change compression techniques for a full-function database:

Unload the data in an expanded format, then change the DPICDS
Change the DPICDS while the data is compressed (before you reorganize the database or after you unload the data in a compressed format)

The scenario that fits your needs may vary from these two, but the following considerations apply regardless:

When changing to Custom Huffman, you must run the Trial utility to register the segments.
When changing to Shared Table or Custom Hardware Dictionary, the table or dictionary must already exist at the RUN level. If not, run the Trial utility to build the table or dictionary, then promote the table or dictionary.

Warning

When making several changes to the DPICDS at one time (such as refreshing tables or dictionaries, changing MSL, or changing techniques), be sure to carefully evaluate the sequential order of the changes. If you promote the table or dictionary inadvertently, you could promote off the table or dictionary needed to expand your existing data. Consequently, we recommend that you back up the DPICDS and DPITBL data sets before starting.

This section contains the following topics:

Changing compression techniques for a full-function database

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