Record Definition Language › Determining the Best Compression

Determining the Best Compression

To determine the best possible compression to implement for a file, you can use the facilities of the IUI. Follow the steps below to determine the best compression obtainable for the file. These steps comprise a summary procedure.

1. Analyze the characteristics of the file.
2. Use the b subcommand on the data set in the worklist to browse the statistics.

You now have a basis on which you can judge the effectiveness of the RDL for each record. Fine-tuning the RDL for a record may increase compression but may increase the CPU overhead.

Note: While RDL is the acronym for Record Definition Language, the term the RDL is commonly used to mean the set of RDL statements which represent the record definition (for compression purposes) for a given data set or pattern. The RDL is located in the Analysis File as an entity within the record for a discrete file or pattern entry and is in the external character format. The RDL is also a subsection of an FDT. The RDL portion of an FDT is in the internal format and describes the record format for the file to be processed under control of this FDT.

You can respecify the RDL for the record and perform the testing procedure again. If you change the RDL for a record, the Byte Distribution Analysis (BDA) for the record is performed again.

As you fine-tune the RDL for the records in the file, follow the steps below, which can be repeated as often as needed until you have obtained the compression that you want to implement for the file.

1. Update the RDL you have devised for the record.
2. Redo the data set analysis.
3. Evaluate the results of the test compression.

When the testing and evaluating have produced the optimum compression controls, follow the step-by-step procedure outlined earlier in this section to implement compression for the file.