Concatenated PDSs are processed with a DSORG=PO in the DCB. When PDSs are concatenated, the system treats the group as a single data set. A partitioned concatenation can contain a mixture of PDSs, PDSEs, and UNIX directories. Partitioned concatenation is supported only when the DCB is open for input.

There is a limit to how many DD statements are allowed in a partitioned concatenation. Add together the number of PDS extents, the number of PDSEs, and the number of UNIX directories in the concatenation. The sum cannot exceed 255. For example, you can concatenate 15 PDSs of 16 extents each with 8 PDSEs and 7 UNIX directories ((15 x 16) + 8 + 7 = 255 extents).

Concatenated PDSs are always treated as having like attributes, except for block size. They use the attributes of the first data set only, except for the block size. BPAM OPEN uses the largest block size among the concatenated data sets. All attributes of the first data set are used, even if they conflict with the block size parameter specified. For concatenated format-F data sets (blocked or unblocked), the LRECL for each data set must be equal.

You process a concatenation of PDSs the same way you process a single PDS, except that you must use the FIND macro to begin processing a member. You cannot use the POINT (or NOTE) macro until after issuing the FIND macro the appropriate member. If two members of different data sets in the concatenation have the same name, the FIND macro determines the address of the first one in the concatenation. You would not be able to process the second one in the concatenation. The BLDL macro provides the concatenation number of the data set to which the member belongs in the K field of the BLDL list. (See BLDL—Construct a Directory Entry List.)