Sharing data spaces through the PASN-AL

One way many problem-state programs with PSW key 8 - F can share the data in a data space is by placing the entry for the data space on the PASN-AL and obtaining the ALET. In this way, the programs can pass the ALET to other problem-state programs in the address space, allowing them to share the data in the data space.

The following example describes a problem-state program with PSW key 8 - F creating a data space and sharing the data in that space with other programs in the address space. Additionally, the program assigns ownership of the data space to its job step task. This assignment allows the data space to be used by other programs even after the creating program's task terminates. In the example, PGM1 creates a 10-megabyte data space named SPACE1. It uses the TTOKEN parameter on DSPSERV to assign ownership to its job step task. Before it issued the DSPSERV CREATE, however, it had to find out the TTOKEN of its job step task. To do this, it issued the TCBTOKEN macro.

TCBTOKEN    TTOKEN=JSTTTOK,TYPE=JOBSTEP
 .
DSPSERV CREATE,NAME=DSNAME,BLOCKS=DSSIZE,STOKEN=DSSTOK,ORIGIN=DSORG,
            TTOKEN=JSTTTOK
ALESERV ADD,STOKEN=DSSTOK,ALET=DSALET,AL=PASN
 .
 .
DSNAME      DC  CL8'SPACE1  '   DATA SPACE NAME
DSSTOK      DS  CL8             DATA SPACE STOKEN
DSALET      DS  F               DATA SPACE ALET
DSORG       DS  F               ORIGIN RETURNED
DSSIZE      DC  F'2560'         DATA SPACE 10 MEGABYTES IN SIZE
JSTTTOK     DS  CL8             TTOKEN OF JOB STEP TASK

Unless PGM1 or a program running under the job step TCB explicitly deletes the data space, the system deletes the data space when the job step task terminates.

Note that when PGM1 issues the ALESERV ADD to add the entry for DS1 to the PASN-AL, the system checks to see if an entry for DS1 already exists on the PASN-AL. If an entry already exists, and a problem-state program with PSW key 8 - F added the entry, the system rejects the ALESERV ADD request. However, PGM1 can still access the data space. The system will simply not create a duplicate entry.