SAS(R) 9.1.3 Companion for z/OS

60 Assigning Multiple Librefs to a Single SAS Data Library Chapter 2
statement or function for a data library that was allocated externally. The following
information describes how SAS determines which engine to use when you do not specify
one. The engine that SAS selects depends on the type of library you are accessing. See
“Library Implementation Types for Base and Sequential Engines” on page 40 for more
information on libraries.
If the library that you specify corresponds to a new or empty z/OS data set, SAS
assigns the default engine specified by the ENGINE= system option unless a sequential
engine must be used. Sequential engines are used for the following situations:
3 The library data set is on a tape device, or it is a subsystem data set managed by
BatchPipes.
3 The DCB characteristics DSORG=PS and RECFM=U are specified for the data set.
If a sequential engine is used, SAS assigns the engine specified by the SEQENGINE=
system option. For empty HFS libraries, SAS assigns the engine specified by the
ENGINE= system option.
If the library data set has already been initialized, or, for HFS, if the library
directory already contains members, SAS generally assigns the engine that has been
used to process the library in the past. The following list contains details about how
SAS assigns engines for the different types of libraries:
direct access bound library
SAS automatically assigns the V5 engine if the library data set has the DCB
characteristic DSORG=DA. Otherwise, SAS reads the library header and assigns
the engine that was originally used to initialize the library.
sequential access bound library
SAS reads the first member header record and assigns the engine that was used to
write the first member of the library.
HFS library
SAS examines the extension of each SAS file in the library directory, because the
extension indicates the engine with which the library member was created. If all
of the SAS files in the directory were created with the same engine, that engine is
assigned to the library. If the SAS files were created using a mix of different
engines, SAS assigns the engine specified by the ENGINE= system option.
hiperspace library
SAS automatically assigns the V9 engine without reading the library header if the
library is a permanent hiperspace library, that is, a library that is backed by a
VSAM linear data set. To access a V6 hiperspace library, you must use the
LIBNAME statement and explicitly specify the V6 engine.
Note: Explicitly identifying the engine with the LIBNAME statement or function
saves system resources. R
Assigning Multiple Librefs to a Single SAS Data Library
You can assign more than one libref to the same SAS data library.
For example, suppose that in two different programs you used different librefs for the
same data libraries. Later you develop a new program from parts of the two old
programs, or you include two different programs with the %INCLUDE statement. In
the new program, you could simply assign the two original librefs to each data library
and proceed.
Any assigned libref can be used to access the data library with the following
exception: if ACCESS=READONLY was specified or implied (by DISP=SHR) for one
assignment, then that libref can only be used to read the library, even though update
access is available to the library through another libref.