Problem data from the linkage stack

The linkage stack is used to identify a program that requested a system service, if the service was entered by a branch instruction.

For example, to see the linkage stack entry that is associated with address space identifier (ASID) X'1A', use the IPCS subcommand:

   SUMMARY FORMAT ASID(X'1a')

The resulting dump for the linkage stack associated with the address space (see Figure 1) shows one entry, as follows:

BAKR STATE ENTRY: A Branch and Stack (BAKR) instruction caused this entry.
SASN..1A and PASN..1A: At the time of the BAKR, the program was not in cross memory mode. When the branching program is not in cross memory mode, secondary address space number (SASN) and primary address space (PASN) are identical. If the program had been in cross memory mode, SASN and PASN would not have been identical.
PSW..070C0000 80FD7618: The return address of the branch caused by the BAKR is FD7618. This address is in the right half of the program status word (PSW).

Figure 1. Example: Viewing a linkage stack entry

LINKAGE STACK ENTRY  01  LSED: 7F7490B0
  LSE: 7F749010
     GENERAL PURPOSE REGISTER VALUES
     00-03.... 7FFEB410  04504DF4  04532000  04541FFF
     04-07.... 04504CE4  81150380  00000028  04504B50
     08-11.... 04503A75  04502A76  04501A77  04504630
     12-15.... 84500A78  00000000  80FD7618  8450FAF8
     ACCESS REGISTER VALUES
     00-03.... 00000000  00000000  00000000  00000000
     04-07.... 00000000  00000000  00000000  00000000
     08-11.... 00000000  00000000  00000000  00000000
     12-15.... 00000000  00000000  00000000  00000000
1S/A ON AQFT PER SYSTEM HUNG 22:30 08/30/88       24  09:42:48 10/14/88

PKM..8000 SASN..001A EAX..0000 PASN..001A PSW..070C0000  80FD7618
    TARG... 8450FB12  MSTA... 0451E300  00000000
    TYPE... 84
     BAKR STATE ENTRY
    RFS... 0F38      NES... 0000

Many system services are called through branches. For branch entry services, use register 14 to identify the calling program. Look for the problem in the calling program. See z/OS MVS Programming: Extended Addressability Guide for more information about the linkage stack.