A catalog alias can have up to four qualifiers. However, the actual number of qualifiers used, or the "multilevel alias search level", is initialized in the SYSCATxx member of SYS1.NUCLEUS or LOADxx member of SYS1.PARMLIB. You can change this level without a system IPL by using the MODIFY CATALOG,ALIASLEVEL command. The change will remain in effect until the next time you IPL the system.

This command can be used to test various multilevel alias search levels. However, you should use this command with care. Changing the search level might result in some data sets becoming inaccessible, since the catalog searched might not be the catalog in which the data set is actually cataloged.

For example, the following aliases might be defined:

In this case, if the original search level were 2, the data set APPLIC1.TESTING.DATA would be cataloged in SYS1.ICFCAT.TESTING. However, if you used MODIFY CATALOG,ALIASLEVEL(1) to change the search level to 1, subsequent requests for this data set would orient the catalog search to SYS1.ICFCAT.APPLIC. This results in a "data set not found" error.

See The Multilevel Alias Facility for more information on the multilevel alias facility.