ABCs of z/OS System Programming Volume 3 - IBM Redbooks

4.24 Partitioned data set extended (PDSE)
CREATION
CONVERSION
USE
Figure 4-34 PDSE structure
SMS
VOLUME
Partitioned data set extended (PDSE)
Partitioned data set extended (PDSE) is a type of data set organization that improves the
partition data set (PDS) organization. It has an improved indexed directory structure and a
different member format. You can use PDSE for source (programs and text) libraries, macros,
and program object (the name of executable code when loaded in PDSE) libraries.
Logically, a PDSE directory is similar to a PDS directory. It consists of a series of directory
records in a block. Physically, it is a set of “pages” at the front of the data set, plus additional
pages interleaved with member pages. Five directory pages are initially created at the same
time as the data set.
New directory pages are added, interleaved with the member pages, as new directory entries
are required. A PDSE always occupies at least five pages of storage.
The directory is like a KSDS index structure (KSDS is covered in 4.34, “VSAM key sequenced
cluster (KSDS)” on page 166), making a search much faster. It cannot be overwritten by being
opened for sequential output.
If you try to add a member with DCB characteristics that differs from the rest of the members,
you will get an error.
There is no longer a need for a PDSE data set to be SMS-managed.
146 ABCs of z/OS System Programming Volume 3
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DATA CLASS CONSTRUCT
DSNTYPE=LIBRARY
// DD DSNTYPE=LIBRARY
DFDSS CONVERT (PDS I PDSE)
BSAM, QSAM, BPAM