Compressing the output image copy

The image copy data sets that are produced by Fast Path Offline Suite functions conform to the standard format which is used by IMS.

You can apply a BMC image copy compression algorithm to reduce the size of the output data set by specifying the COMPRESSION keyword. Compressed image copies are fully compatible with all BMC IMS products (such as RECOVERY PLUS for IMS), but must be expanded before they can be used by products other than those of BMC.

COMPRESSION=NONE (the default) specifies that the output image copy data set is not compressed.

A BMC compression algorithm can be selected using any of the other available values for the COMPRESSION keyword:

  • COMPRESSION=FSE (free space element elimination) does not write free space elements or free blocks to the output. No other compression is performed.

  • COMPRESSION=CCC (common character compression) compresses repeating groups of low-values, high-values, zeros, blanks, or combinations of these characters. Free blocks are not written to the output. This option compresses the prefix and key portions of the database records, if possible.

  • COMPRESSION=DPE (full character compression) compresses all character types using a subset of the BMC DATA PACKER/IMS product. Free blocks are compressed and written to the output. This option compresses the prefix and key portions of the database records, if possible.

The example below requests the creation of three output image copies. The first image copy is not compressed. The second image copy data set is compressed by using the FSE algorithm. The third image copy data set is compressed by using the CCC algorithm.

IMAGECOPY  IAREA=areaname
 IC  DDNAME=ddname1,COMPRESSION=NONE
 IC  DDNAME=ddname2,COMPRESSION=FSE
 IC  DDNAME=ddname3,COMPRESSION=CCC
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