Because a member of a PDS is sequentially organized, it is processed in the same manner as a sequential data set. To locate a member or to process the directory, several macros are provided by the operating system. The BLDL macro can be used to read one or more directory entries into virtual storage. The FIND macro locates a member of the data set and positions the DCB for subsequent processing. The STOW macro adds, deletes, replaces, or changes a member name in the directory. To use these macros, you must specify DSORG=PO or POU in the DCB macro. Before issuing the FIND, BLDL, or STOW macro, you must check all preceding I/O operations for completion.