Procedure for Choosing a Multilevel Alias

You should take these steps before defining new aliases:

Do a LISTCAT LEVEL, using only the first qualifier of the new alias. For example, if the new alias is A.B.C, execute LISTCAT LEVEL(A). For aliases of only one level, the "first" qualifier is the alias name.
Check for any matches. If there are any matches and the listed data set does not currently reside in the catalog you are attempting to define the alias for, you might need to rename the data set or choose another alias if the data set becomes inaccessible.

For example, if you want to define the alias A.B for ICFUCAT2, use LISTCAT LEVEL(A) and analyze the output. In this example, A is an alias for ICFUCAT1 and A.B.C is an alias for ICFUCAT3:

    CLUSTER ------ A.CLUSTER
         IN-CAT -- ICFUCAT1
    DATA --------- A.DATA
         IN-CAT -- ICFUCAT1
    CLUSTER ------ A.B.CLUSTER2
         IN-CAT -- ICFUCAT1
    DATA --------- A.B.DATA2
         IN-CAT -- ICFUCAT1
    CLUSTER ------ A.B.CLUSTER
         IN-CAT -- ICFUCAT1
    DATA --------- A.B.DATA
         IN-CAT -- ICFUCAT1
    CLUSTER ------ A.B.C.CLUSTER
         IN-CAT -- ICFUCAT3
    DATA --------- A.B.C.DATA
         IN-CAT -- ICFUCAT3
    INDEX -------- A.B.C.INDEX
         IN-CAT -- ICFUCAT3
    ALIAS -------- A
         IN-CAT -- ICFMASTR
    ALIAS -------- A.B.C
         IN-CAT -- ICFMASTR

Evaluation of the LISTCAT output:

The data sets A.CLUSTER and A.B.C.CLUSTER and their components will remain accessible. With an alias search level of 3, their aliases (A and A.B.C) continue to be oriented to the correct catalog.
However, A.B.CLUSTER2 and A.B.CLUSTER will become inaccessible if you define A.B as an alias for ICFUCAT2. These data sets are cataloged in ICFUCAT1, since they use the alias "A". After alias A.B is defined, searches for these data sets will be oriented to ICFUCAT2, and the data sets will not be found.

If you choose to rename a data set, the data and index components probably need to be renamed as well.

The following types of data sets might not be found by LISTCAT LEVEL:

Data sets defined with a catalog specified in the CATALOG parameter (bypassing the catalog search order) or with job or step catalogs.
Data sets whose data or index component names were defined by the user.
Data sets that became inaccessible because of the removal of an alias.

To identify data sets not cataloged according to catalog aliases, use the CATALOG parameter of LISTCAT, specifying the catalog containing the data set's entry. All user data sets should be cataloged according to catalog aliases. Otherwise, data can easily become lost, defeating the purpose of cataloging data.