CMS File System: Packed Files

CMS has the concept of a packed file. These are files that have be compressed using the PACK option of the CMS COPYFILE command, or by using the SET PACK ON command in XEDIT.

What makes packed files a bit unusual is that the support for it isn't imbedded in the file system itself. It's really just a specific file format. The low-level CMS file system read/write APIs aren't performing the unpack/pack operation. It's in the application that's reading or writing the files.

Since most CMS applications (and CMS commands) don't understand the packed file format, you have to unpack the file before you read it.

If you download and install the HSX package from the VM Download Library into your CMS environment, it will intercept the file system APIs and handle the pack/unpack operations transparently.

Format

UNDER CONSTRUCTION

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