Friday, July 27, 2007

Packed datasets

Packed data is data in which ISPF has replaced any repeating characters with a sequence showing how many times the character is repeated. Packing data allows you to use direct access storage devices (DASD) more efficiently because the stored data occupies less space than it would otherwise.

If the source data that you want to process is packed, it must be expanded before it can be successfully processed by any of the language processors. The expansion method you should use depends on whether your source data is:

=>A sequential dataset that contains expansion triggers:

An expansion trigger is a keyword that tells ISPF to expand additional data before copying, including or imbedding it in the source data. ISPF does not recognise expansion triggers in data stored as a sequential dataset. Therefore, for these types of datasets,

1. Manually expand the data: Edit the source data and enter PACK OFF
2. Select the Source Data Packed option before calling one of the language processors.

=>Either of the following:
A. A Sequential dataset that does not contain expansion triggers
B. Any member of a partitioned dataset, either with or without expansion triggers.

ISPF does recognize expansion triggers in data stored as members of a partitioned data set. Also, if your source data does not contain expansion triggers, you do not have to be concerned with them. Therefore, for these two types of data, select the Source Data Packed option before calling one of the language processors.

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