COMPAKTOR Overview

COMPAKTOR provides an efficient and easy-to-use method of reorganizing a DASD volume, positioning data sets or releasing unused space within data sets. It does this via a simple one-step process, with a minimum of JCL and control statements required.

Features

• Reduction of Free Space Fragmentation - On most volumes, CPK drastically reduces the number of free space areas, through contiguous placement of data sets.
• Merging of Data Set Extents - Most multi-extent data sets are merged into a single extent by COMPAKTOR.
• Data Set Positioning - COMPAKTOR has a flexible and convenient feature for user-specified data set placement.
• Elimination of Unused Data Set Space - A user may free all or part of the unused space within Physical Sequential (PS), partitioned (PO), and/or VSAM data sets. The freeing of space can be done during COMPAKTion or as an independent option of CPK (TYPE=RLSE).
• VTOC Position and Size - COMPAKTOR allows you to change the position and size of the VTOC. This can only be done by a COMPAKT-from-backup, not a FASTCPK.
• VTOC Analysis - COMPAKTOR always performs a complete analysis of a VTOC, often detecting structural VTOC errors not detected by any IBM software. Any errors detected result in diagnostic messages. Under some conditions, CPK even corrects VTOC errors.
• Error Free VTOCs - After a successful COMPAKTion, all reorganized DASD volumes have error-free VTOCs. The volume free space is accurate.
• Volume Maps - CPK provides track maps of DASD volumes, in track sequence. Maps of a volume both BEFORE and AFTER COMPAKTion are automatically provided. CPK also provides a summary report on the status of the volume.
• Mapping Feature - As an option, you can request that CPK only map a volume. The volume may be a DASD volume residing on a direct-access device or an FDR backup of a DASD volume residing on a tape or sequential file on DASD. Full VTOC analysis is still performed.
• Simulation Feature - This feature provides full maps of a DASD volume both BEFORE and AFTER reorganization or release. However, no actual COMPAKTion is performed and the volume is never modified.
• Multiple Volume Functions - For most functions, COMPAKTOR can process multiple DASD volumes in one execution. Multiple DASD volumes can be specified as a list of volume serials, a volume serial prefix, or all online DASD volumes can be requested. The required online DASD volumes are dynamically allocated.

Fast COMPAKTION In-Place

If TYPE=FASTCPK is specified on the COMPAKT control statement, COMPAKTOR does a “COMPAKT-in-place” on one or more DASD volumes, without taking or requiring an FDR backup. For each volume processed, COMPAKTOR analyzes the dumped VTOC and builds an internal map of the DASD volume. A number of algorithms are then used to determine the “best” way of organizing the DASD volume, and a new internal map is built; this new map is of the reorganized, or COMPAKTed, DASD volume. User-specified data set placement or space release requests are honored during these algorithms.

COMPAKTOR moves tracks to their new locations according to the new volume organization map. Once this has been successfully done, COMPAKTOR rebuilds the extent information contained in the VTOC (and, if necessary, the VVDS).

FASTCPK achieves almost the same level of free space consolidation and reduction of multi-extent data sets as COMPAKTion-from-backup, without compromising the integrity of your data. FASTCPK maintains a log of its processing and provides an automatic recovery function that allows COMPAKTion to be restarted if the operating system or the job fails.

Fast COMPAKTion requires that there be at least a small amount of free space on the volume, in order to allocate a “recovery” data set used to keep track of COMPAKTOR's progress and allow restart if COMPAKTOR is prevented from completing its data movement.

FASTCPK supports most of the features of COMPAKTOR, except that you cannot change the size or location of the VTOC, VVDS, or active indexed VTOC.

Space release

If TYPE=RLSE is specified on the COMPAKT control statement, COMPAKTOR makes a special run whose only purpose is to release space from PS, PO, and VSAM data sets. TYPE=RLSE does not move any data sets or attempt to reduce fragmentation or increase the size of free space. It does not require a backup of the DASD volume; it simply reads the VTOC from the DASD volume, manipulates it to release space as indicated by CPK options, and updates the VTOC in place. A TYPE=RLSE step usually runs in just a few seconds.

COMPAKTOR prints the name of each data set selected and the number of tracks released from each.