SAS(R) 9.1.3 Companion for z/OS

62 Using Multivolume SAS Data Libraries Chapter 2
For example, suppose that a SAS data library with the libref MYLIB is stored
in the z/OS data set MYID.RECENT.DATA. The following two statements would
clear the libref and deallocate the library data set:
libname mylib clear;
x free da(’myid.recent.data’);
CAUTION:
Do not attempt to release the allocation for a library data set without first
deassigning the libref. R
3 You can deassign a SAS data library in the SAS Explorer window by selecting the
DELETE menu.
Using Multivolume SAS Data Libraries
A direct access bound library or sequential access bound library on disk can extend to
more than one volume. The library data set might exist on multiple DASD volumes, but
it is processed by SAS software as one logical entity. This capability greatly increases
the storage capacity of a data library. This section discusses two separate
methodologies for creating and extending multivolume data libraries:
Requesting Space As Needed
This approach is recommended for its simplicity, flexibility, and efficiency. With
this methodology, you do not need to determine in advance the amount of storage
that a data library will require. SAS can request additional DASD extents
(allocations of contiguous disk space) as the library needs to grow, meanwhile
leaving more DASD space available for other applications. This approach allows
storage management subsystem (SMS) and third-party DASD space management
to automatically make the optimum decisions about volume selection, and so forth.
PreAllocating Space
In some circumstances, such as when entire volumes have been set aside for use
by a particular application, it is more convenient to preallocate the library data
set. This approach allows more control, but it requires more effort in planning to
estimate the size of the SAS data sets that will reside in the library.
General Guidelines
Following is a short summary of the main rules that govern allocation of space for
SAS data libraries on disk. This summary is not intended to address all points of this
broad subject. For additional information, see IBM documentation as well as manuals
for any third-party DASD space management software installed on z/OS at your site.
Both direct access and sequential access bound libraries reside in a data sets with
the attribute DSORG=PS. On disk, these data sets can be extended to as many as 59
volumes. Each time space is requested for a library data set, the disk space is supplied
in one or more chunks of contiguous space termed extents. A regular format
DSORG=PS data set can have up to 16 extents per volume. Extended format
DSORG=PS data sets can have as many as 123 extents per volume, but they can only
be used for sequential access bound libraries.
When allocating a new library data set, you must specify the size of the initial
(primary) disk space allocation as well as the size of the extent (secondary) to be
obtained when the library data set needs to be enlarged. Each request to extend the
size of the library data set will be satisfied by a secondary extent on the current last