ISPF ALTLIB

Refer : http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/IKJ4C310/BACK_1.1?SHELF=IKJ4BK20&DT=20010706113306

The ALTLIB command offers several functions, which you specify using the following operands:


ACTIVATE
Allows implicit execution of execs in a library or libraries on the specified level(s), in the order specified.

DEACTIVATE
Excludes the specified level from the search order.

DISPLAY
Displays the current order in which exec libraries are searched for implicit execution.

RESET
Resets searching to the system level only (execs allocated to SYSEXEC or SYSPROC).


For complete information about the syntax of the ALTLIB command, see z/OS TSO/E Command Reference.
Notes:


1. With ALTLIB, data sets concatenated to each of the levels can have differing characteristics (logical record length and record format), but the data sets within the same level must have the same characteristics.

2. At the application and system levels, ALTLIB uses the virtual lookaside facility (VLF) to provide potential increases in library search speed.



Under ISPF, ALTLIB works the same as in line mode TSO/E. However, if you use ALTLIB under line mode TSO/E and start ISPF, the alternative libraries you specified under line mode TSO/E are unavailable until ISPF ends.

When you use ALTLIB under ISPF, you can pass the alternative library definitions from application to application by using ISPEXEC SELECT with the PASSLIB operand; for example:




ISPEXEC SELECT NEWAPPL(ABC) PASSLIB


The PASSLIB operand passes the ALTLIB definitions to the invoked application. When the invoked application completes and the invoking application regains control, the ALTLIB definitions that were passed take effect again, regardless of whether the invoked application changed them. If you omit the PASSLIB operand, ALTLIB definitions are not passed to the invoked application.



Examples of the ALTLIB Command

In the following example, an application issues the ALTLIB command to allow implicit execution of execs in the data set NEW.EXEC, to be searched ahead of SYSPROC:




ALTLIB ACTIVATE APPLICATION(exec) DATASET(new.exec)


The application could also allow searching for any private execs that the user has allocated to the file SYSUEXEC or SYSUPROC, with the following command:



ALTLIB ACTIVATE USER(exec)


To display the active libraries in their current search order, use the DISPLAY operand as follows:



ALTLIB DISPLAY


For more information about the search order EXEC uses for execs and CLISTs, see z/OS TSO/E Command Reference.
To deactivate searching for a certain level, use the DEACTIVATE operand; for example, to deactivate searching for execs on the system level (those allocated to SYSEXEC or SYSPROC), issue:




ALTLIB DEACTIVATE SYSTEM(exec)


And, to reset exec searching back to the system level, issue:



ALTLIB RESET