SAS(R) 9.1.3 Companion for z/OS

R
Using SAS Data Libraries Sequential Access Bound Libraries 45
libname seqdisk tape ’user489.seqdisk.saslib’ disp=(new,catlg)
unit=(3390,3) space=(cyl,(200,200)) blksize=27998;
data seqdisk.memb01;
...
Note:
3 To ensure the most complete use of the DASD track, specify the optimum
half-track BLKSIZE for the type of disk device used. For sequential access bound
libraries, this must be specified on the DD or LIBNAME statement. The SAS
BLKSIZE system options are not used for sequential access bound libraries.
3 The maximum number of disk volumes to which the library data set can extend is
governed by the unit count in the examples above.
3 Sequential access bound libraries can reside in extended format sequential data
sets. Extended format sequential data sets can be defined as compressed by SMS,
and they can also occupy more than 64K tracks per volume.
General Usage Notes
3 Due to the nature of sequential devices, SAS allows only two types of operations
with members of a sequential bound library: reading an existing member and
writing a new copy of a member to the library. The following types of operations
are not supported for sequential access bound libraries:
3 having multiple members in the library open at the same time
3 updating the contents or attributes of a member of the library
3 renaming or deleting a member of the library.
3 When the FILEDISP=NEW data set option is specified for a member to be written
to a sequential access bound library, SAS will replace all of the members that
previously existed in the library, even if they were protected by an ALTER
password. The ALTER password is not checked even for the member being
replaced.
3 When the COPY procedure is used to write members to a sequential access bound
library, the rules regarding member replacement (listed above) apply only to the
first member being processed by a COPY statement or PROC COPY invocation.
All other members involved in the COPY operation are appended to the end of the
library data even if they already exist in the library. Therefore, it is possible to
cause a library to contain two copies of the member, only the first of which will be
recognized. You should plan all COPY operations carefully so that you avoid this
outcome.
3 SAS locates members of sequential access bound libraries by sequentially scanning
the library from the current location (usually the beginning of the library data set)
until the member is located. To avoid the excessive I/O that could occur with this
type of operation, members of these libraries, that will be repeatedly accessed in a
SAS job/session, should be first copied to a BASE engine library and then copied
from the BASE engine library to the sequential access bound library in one PROC
COPY operation. This is particularly important when appending to large
multivolume tape libraries.
3 When adding members to an existing sequential access bound library on tape, SAS
can read the library to determine which engine format to use. However,
determining the engine format requires an extra tape mount if the library is
internally assigned. By explicitly specifying the engine, you can avoid this extra
tape mount.