All the options discussed in this section are alterable, except for RECORDSIZE. If you decide your initial selection is inappropriate, you can use the access method services ALTER command to change it.

Buffers

You can specify buffer size on three different parameters:

BUFFERSPACE

The required buffer space for your catalog is determined by catalog. You only need to specify this if you want extra buffer space for your catalog. In general, allow catalog to determine buffer space. The number of buffers specified applies to each processor.

BUFND

Specifies the number of buffers for transmitting data between virtual and auxiliary storage. The default, STRNO+1, is usually adequate. When a catalog contains large GDGs or other spanned records, the number should be increased accordingly to a minimum of MAXLRECL/CISIZE+STRNO.

BUFNI

Specifies the number of buffers for transmitting index entries between virtual and auxiliary storage. The default, STRNO+2, is adequate for 3 levels of index in the catalog. If the catalog index exceeds 3 levels of index, the minimum BUFNI equals the number of levels of index - 1 + STRNO.

FREESPACE

The free space allows catalog updates without an excessive number of control interval and control area splits.

The following parameter affects catalog performance but can only be specified when the catalog is initially defined.

RECORDSIZE

The record size information is ignored when a catalog is defined. It will always set the record size information for a catalog as though RECORDSIZE(4086 32400) was specified. The maximum value should always be the default if large records could be generated. Large catalog records are generated for GDGs that have many GDSs. Master catalogs with user catalog connector records that contain a large number of aliases also have large catalog records.