GIMUNZIP processing

The GIMUNZIP service routine extracts data sets and files from the archive files that compose the GIMZIP package. An archive file consists of a portable image of a data set or file and the information needed to reload the data from the portable image (see Archive files for details on archive file contents and construction).

GIMUNZIP uses the UNIX System Services pax command to expand the following component files from an archive file temporarily into a UNIX file system:

the portable image of the original data set or file, and
the file attribute file that contains the information necessary to reload the data from the archived data set or file.

GIMUNZIP then reads the file attribute file and uses the information recorded there, along with information specified on the <ARCHDEF> tag, such as volume, newname, or prefix, to allocate a new or existing data set or file. The portable image of the original data set or file is stored in the data set or file just allocated for that purpose.

When GIMUNZIP encounters a package that contains archive segments, GIMUNZIP reassembles the archive segments into the original archive form, optionally verifies the integrity of the archive, and recreates the original data.

If the HASH=YES option was specified, then GIMUNZIP performs SHA-1 hash checking for the archive files. Specifically, GIMUNZIP reads the package attribute file for the package. The package attribute file, GIMPAF.XML, is found in the package directory, and contains the known hash values for the archives. These hash values were recorded by GIMZIP when the package and archives were created. GIMUNZIP then uses either ICSF services or Java™ 2 programs to compute the current hash values for the archive files, and compares this value to the known hash values for the archive files.

If the computed hash value matches the known hash value, then the integrity of the archive file is ensured. However, if the computed hash value does not match the known hash value, GIMUNZIP processing stops. This condition indicates that the archive file was corrupted after it was produced by GIMZIP when the package was created.