1. A method, comprising determining, via a processor, a user catalog that has a greater amount of available space in comparison to other user catalogs of a plurality of user catalogs, wherein there is a lesser amount of contention among a plurality of threads or processes to access the determined user catalog in comparison to the other user catalogs, and wherein the user catalog is used to store a new data set; subsequent to determining the user catalog, inserting in a group table, an entry that indicates a data set name corresponding to the new data set and an index to the determined user catalog; directing requests for any data sets to the group table; and moving the new data set to another user catalog, in response to an error caused by the determined user catalog.