Example - Using STORMAP with the EXTSET Option

Suppose you want to generate storage information whenever you execute a specific BALR instruction. You can use the STORMAP command with the EXTSET option and the CP TRACE command, in addition to other commands, to produce information about the amount of free storage available each time the BALR instruction is executed.

The following example shows you how this debugging works: 
stormap (extset 250
Ready;
loadmod sttest
Ready;
progmap
Name        Entry       Origin      Bytes        Attributes
STTEST      013E6DB0    013E6DB0    00000250    Amode 31  Reloc
Ready;
d i13e6db0.10
R013E6DB0  LR    18CF         LA    41500005     L     58F0C244     E6
R013E6DBA  BALR  05EF         BCT   4650C006
Ready;
trace inst pswa 13e6dba run cmd ext 250
Ready;
start
DMSLIO740I Execution begins...
 -> 013E6DBA  BALR  05EF     -> 013E6FBA    CC 1
                                   Storage Map
                                  ------- ---
 VMSIZE       NUCALPHA     NUCSIGMA     NUCOMEGA     NUCPHI       NUCCHI
01400000     00F00000     00F52A00     01300000     01000000    012CF5C8
                           Unallocated Free Storage Queue
                          ----------- ---- ------- -----
       <16MB                      >16MB
Total       Largest        Total       Largest      Total Unallocated
00D2B000    00D1E000       003E1000    003DB000     0110C000
 -> 013E6DBA  BALR  05EF     -> 013E6FBA    CC 2
                                   Storage Map
                                  ------- ---
 VMSIZE       NUCALPHA     NUCSIGMA     NUCOMEGA     NUCPHI       NUCCHI
01400000     00F00000     00F52A00     01300000     01000000    012CF5C8
                           Unallocated Free Storage Queue
                           ----------- ---- ------- -----
      <16MB                      >16MB
Total       Largest        Total       Largest      Total Unallocated
00D2B000    00D1E000       003DF000    003DB000     0110A000
 -> 013E6DBA  BALR  05EF     -> 013E6FBA    CC 2
                                   Storage Map
                                   ------- ---
VMSIZE       NUCALPHA     NUCSIGMA     NUCOMEGA     NUCPHI       NUCCHI
01400000     00F00000     00F52A00     01300000     01000000 012CF5C8
                           Unallocated Free Storage Queue
                           ----------- ---- ------- -----
      <16MB                      >16MB
Total       Largest        Total       Largest      Total Unallocated
00D2B000    00D1E000       003DD000    003DB000     01108000
 -> 013E6DBA  BALR  05EF     -> 013E6FBA    CC 2
                                   Storage Map
                                   ------- ---
 VMSIZE       NUCALPHA     NUCSIGMA     NUCOMEGA     NUCPHI       NUCCHI
01400000     00F00000     00F52A00     01300000    01000000 012CF5C8
                           Unallocated Free Storage Queue
                           ----------- ---- ------- -----
       <16MB                      >16MB
Total       Largest        Total       Largest      Total Unallocated
00D2B000    00D1E000       003DB000    003D9000     01106000
 -> 013E6DBA  BALR  05EF     -> 013E6FBA    CC 2
                                   Storage Map
                                   ------- ---
 VMSIZE       NUCALPHA     NUCSIGMA     NUCOMEGA     NUCPHI       NUCCHI
01400000     00F00000     00F52A00     01300000     01000000 012CF5C8
                           Unallocated Free Storage Queue
                           ----------- ---- ------- -----
       <16MB                      >16MB
Total       Largest        Total       Largest      Total Unallocated
00D2B000    00D1E000       003D9000    003D7000     01104000 Ready;
The following steps describe the procedure illustrated in the previous example:
  • The STORMAP command generates summary information whenever an external interrupt X'250' is reflected to the virtual machine. This external interrupt corresponds to CMD EXT 250 set in the TRACE instruction issued later.
  • The LOADMOD command loads your STTEST program.
  • The PROGMAP command determines where in storage STTEST is loaded.
  • After you know the load point, 013E6DB0, the CP DISPLAY I command locates the BALR instruction. This is the instruction you want to trace.
  • Then, the CP TRACE command sets a trace for the BALR instruction. The RUN option causes execution to continue when the BALR is executed. The CMD EXT X'250' generates an external interruptX'250' when the BALR is executed. This external interrupt corresponds to the EXTSET 250 option set on the STORMAP command issued earlier.
  • The START command starts execution of STTEST. The result is that each time the BALR is executed, an external interrupt X'250' is generated which in turn displays the storage information.

The data shows that the total amount of unallocated storage above 16 MB is reduced by two pages on each BALR call. You now have to determine if this loss of two pages is a normal condition on that call.

After you know the meaning of the fields in the summary report, you can reduce the amount of data displayed by using the NOHEAD option on the STORMAP command. For example: 
stormap (nohead extset 255
Ready;
d i13e6910.10
R013E6910  LR    18CF         LA    41500005     L     58F0C244     E6
R013E691A  BALR  05EF         BCT   4650C006
Ready;
trace inst pswa 13e691a run cmd ext 255
Ready;
start
DMSLIO740I Execution begins...
 -> 013E691A  BALR  05EF     -> 013E6B1A    CC 1
01400000     00E00000     00FEB158     01000000
00D2B000    00D1E000       003CD000    003CB000     010F8000
 -> 013E691A  BALR  05EF     -> 013E6B1A    CC 2
01400000     00E00000     00FEB158     01000000
00D2B000    00D1E000       003CB000    003C9000     010F6000
 -> 013E691A  BALR  05EF     -> 013E6B1A    CC 2
01400000     00E00000     00FEB158     01000000
00D2B000    00D1E000       003C9000    003C7000     010F4000
 -> 013E691A  BALR  05EF     -> 013E6B1A    CC 2
01400000     00E00000     00FEB158     01000000
00D2B000    00D1E000       003C7000    003C5000     010F2000
 -> 013E691A  BALR  05EF     -> 013E6B1A    CC 2
01400000     00E00000     00FEB158     01000000
00D2B000    00D1E000       003C5000    003C3000     010F0000
Ready;

The third token of the second line of data after each BALR is reduced by two pages. From our previous example, you know this field is for unallocated storage above 16 MB.

Note: Remember, you can also use the FILE APPEND option to write the data to the

STORMAP DATA A file rather than to the console.