The constant creation, deletion, extension and reduction of files during active operation means that the free storage space and the files created on the volumes of a pubsets become increasingly fragmented. This fragmentation increasingly impairs file access performance and the uniform distribution of the I/O load to the volumes on the pubset. The Extents list in the catalog entries becomes longer because of the unavoidable creation of large numbers of small file extents when files are extended.
SPACEOPT
The software product SPACEOPT makes it possible to reduce fragmentation by optimally reorganizing the file extents on a pubset’s volumes. The purpose of SPACEOPT is to create the largest possible continuous free storage areas on a volume so that large files can be allocated with only a small number of extents. In addition, the number of extents is reduced wherever possible by combining multiple small extents to form a single large extent. This results in improved file access performance. Large, continuous areas of free storage space are created on a pubset’s volumes and the danger of an extent list overflow in the catalog entries is eliminated.
SPACEOPT is described in the manual of the same name [52].
HSMS
A pubset can be reorganized by performing a backup and subsequent restoration.
The following HSMS statement can be used to write back all the files in a continuous form and the reorganize the storage space:
//RESTORE-FILES REPLACE-FILES-AND-JV=*YES(REORGANIZE-SPACE=*YES)
If the operand RELEASE-UNUSED-SPACE=*YES is also specified, further storage space is saved: the assigned (allocated), but as yet unused, pages after the file’s “last page pointer” are released.