Ideally, a catalog should be defined with enough space so that it does not grow into secondary extents. Excessive secondary extents can decrease catalog performance. You only need to consider reorganizing the catalog to eliminate secondary extents if their number becomes excessive.

A catalog can have up to 123 extents but can only occupy space on a single volume.

Before defining a catalog, carefully consider how that catalog will be used. Estimate the number of data sets and OAM object collections that will be defined in the catalog. The size of the catalog is directly affected by the number of entries in the catalog, and by whether you are using the Storage Management Subsystem.