Analyze DB2 storage by using the SM options
The DB2® dump formatter provides a way to analyze the usage of DB2 storage with the Storage Manager (SM) options. Each level of the SM option provides more detailed information than the previous level.
Table 1 summarizes the information generated for each value of SM and for SMSA.
All storage manager reports show information about local storage, global storage (z/OS® CSA/ECSA), and EDM pool statistics.
To obtain the simplest local storage report, run the DSNWDMP statement with SM=1. The local storage report is divided into two sections: one for fixed storage and one for variable storage. Fixed storage is storage that has a predetermined length, and each element has the same length.
The following example shows a local storage report that is generated for the following DSNWDMP statement:
DSNWDMP 'SUBSYS=VA1A,SM=1'==Storage (Local) VARIABLE POOLS
PHB Subpool name F/V CL SP
--- ------------ --- -- --
1 2 3 4 5 6
7E9CB630 ADMF AGL 31 .pA. Var 136K 12 229
66D109C0 ADMF AGL 31 .\.. Var 0K 12 229
50C22EC0 ADMF AGL VL .Z.. Var 28K 12 229
589B7D90 ADMF AGL VL .... Var 180K 12 229
7E9BF7F0 ADMF AGL VL '... Var 56K 12 229
7E983AB0 ADMF AGL VL '.!. Var 28K 12 229
7E97CB20 ADMF AGL 31 'm.. Var 992K 12 229
7E968C60 ADMF AGL 31 '.N. Var 1204K 12 229| Figure Label | Description |
|---|---|
| 1 | Pool header block address |
| 2 | Pool name |
| 3 | Fixed (fix) or variable (var) storage |
| 4 | Size of pool |
| 5 | DB2 storage class |
| 6 | z/OS subpool |
When you specify SM=1, DSNWDMP also generates storage statistics. The following shows an example of a storage statistics report.
Storage statistics
------------------
QSSTGPLF Get Fixed length pool in dataspace 149 QSSTGPLV Variable pool getmains 1081508
QSSTFPLF Free Fixed length pool in dataspace 72 QSSTFPLV Variable pool freemains 1076402
QSSTFREF Fixed pools 6 QSSTFREV Variable pools 570252
QSSTEXPF Fixed pool extensions 5153 QSSTEXPV Variable pool extensions 924971
QSSTCONF Fixed contracted blocks 748 QSSTCONV Variable contracted blocks 333901
QSSTGETM Getmains(GETM) 190487 QSSTFREM Freemains (GETM) 188142
QSSTRCNZ Non RC=0 Getmains 0 QSSTCRIT Short on storage 10812
QSSTCONT Contractions initiated 11238 QSSTABND Abends due to insufficient storage 51To obtain a local storage report with SHB control blocks, run the DSNWDMP statement with SM=2. In a fixed storage pool, the storage always follows the SHB, so only the SHB address is listed in the report. Each block of variable storage has a varying length. With variable storage, the SHB is not in the same place as the storage, so the address of the storage is listed after the address of the SHB.
The following shows an example of a local storage report that is generated for the following DSNWDMP statement:
DSNWDMP 'SUBSYS=VA1A,SM=2,SMSA=2D'==Storage (Local) VARIABLE POOLS
PHB Subpool name F/V CL SP
--- ------------ --- -- --
7E9CB630 ADMF AGL 31 .pA. Var 136K 12 229
SHB: 65BC2D88 52A32000 136K
66D109C0 ADMF AGL 31 .\.. Var 0K 12 229
50C22EC0 ADMF AGL VL .Z.. Var 28K 12 229
1 2 3
SHB: 50CB8B08 2CA5A000 16K
SHB: 50CB8AB8 5089F000 8K
SHB: 50CB8A18 50A3A000 4K | Figure Label | Description |
|---|---|
| 1 | SHB address |
| 2 | Address of storage that SHB relates to |
| 3 | Length of storage |
Within a storage pool, the sum of the segment (SHB) lengths should always equal the length that is described by the pool header block (PHB). In the previous example, the PHB length, 32 KB, is equal to the sum of the SHB lengths: 12 KB+8 KB+8 KB+4 KB.
Use SM=4 and SM=5 to check for fragmentation within blocks and storage use within individual variable storage pool blocks. The report includes the total length of allocated and free elements for each segment of storage and the total for the storage pool. The total for the storage pool appears after the last SHB for the pool.
The following shows an example of a local storage report that is generated for the following DSNWDMP statement:
DSNWDMP 'SUBSYS=VA1A,SM=4,SMSA=2D'Jobname VA1ADBM1 ASID(002D)
==Storage (Local) FIXED POOLS
PHB Subpool name F/V CL SP
--- ------------ --- -- --
7F7594B8 EDM FIXED LENGTH POOL Fix 4K 12 229
SHB: 7F2DE000 4K
7F759518 EDM FIXED LENGTH POOL Fix 4K 12 229
SHB: 7F0AF000 4K
7F759810 RDS STPM LOCAL POOL Fix 0K 12 229
7F75B290 SHBS FOR LOCAL V-POOLS Fix 4K 12 229
SHB: 7F705000 4K
==Storage (Local) VARIABLE POOLS
PHB Subpool name F/V CL SP
--- ------------ --- -- --
7F2C4510 ADMF AGENT LOCAL POOL Var 32K 12 229
SHB: 7F705AD8 7EF50000 12K Free: 00000578 1K Alloc: 00002A48 10K
SHB: 7F705AB8 7EF53000 8K Free: 00001FD0 7K Alloc: 00000000 0K
SHB: 7F7059D8 7EF6B000 8K Free: 000003E0 0K Alloc: 00001BD0 6K
SHB: 7F7059B8 7EF80000 4K Free: 00000160 0K Alloc: 00000E20 3K
Total: Free: 00002A88 10K Alloc: 00005438 21KUse SM=5 to display the first 16 bytes, with their hexadecimal equivalents, of each allocated element. For the module that made a request to DB2 storage manager for storage, DSNWDMP attempts to display the following extra information:
- The owner token for the storage
- The CSECT and offset within the CSECT of the storage allocation request
- The maintenance level of the module
It is not always possible to determine the CSECT name. Therefore, this name might be incorrect or absent in some cases.
The following shows an example of a local storage report that is generated for the following DSNWDMP statement:
DSNWDMP 'SUBSYS=VA1A,SM=5,SMSA=2D'==Storage (Local) VARIABLE POOLS
PHB Subpool name F/V CL SP
--- ------------ --- -- --
7E9CB630 ADMF AGL 31 .pA. Var 136K 12 229
1 2 3
52A53F88: 00000060 20B20058 D7C3C220 00000000 00000000 ....PCB......... 00000000 DSNB1REL +0D25 12.28
SHB: 65BC2D88 52A32000 136K Free: 00021F60 135K Alloc: 00000060 0K
Total: Free: 00021F60 135K Alloc: 00000060 0K
66D109C0 ADMF AGL 31 .\.. Var 0K 12 229
50C22EC0 ADMF AGL VL .Z.. Var 28K 12 229
2CA5A080: 00000048 201C003C E2E3C1C3 00000000 00000000 ....STAC........ 2FE99C30 DSNIALLI +2387 15.28
2CA5A0D8: 00000038 001C0030 C9D8E4C5 00000000 2FE99C30 ....IQUE.....Z.. 2FE99C30 DSNIALLI +1A33 15.28
2CA5A120: 00003EC8 20FE3EC0 C4D4E3D9 2CA5A160 2CA5B860 ...{DMTR.v~-.v.- 2FE99C30 DSNIALLI +174D 15.28 | Figure Label | Description |
|---|---|
| 1 | Owner token for the storage |
| 2 | CSECT and offset of the storage allocation request |
| 3 | Maintenance level |
You can specify DS options with SM options to display storage information by thread. This information includes the short, long and vlong pool addresses. These addresses are addresses of storage pools within the DBM1 address space.
The following shows an example of a storage report that is generated for the following DSNWDMP statement:
DSNWDMP 'SUBSYS=VA1A,DS=1,SM=5,SMSA=2D'This example shows that a CICS® thread signed on as user USRT001, running plan TSTA85, on correlation ID PT01XA85 is using ADMF local pool 7F2C4510. The thread uses 32 KB of storage, of which 21 KB is currently allocated.
Jobname CICS41F ASID(0021)
ACE: 0624C008 Status: T Req: 0003 Allied Chain
CT: 7F2E5030 Short: 7F2C43C0 Long: 7F2C43C0 Vlong: 7F2C4350
Authid: USRT001 Plan: TSTA85 Corrid: PT03XA85 Corrname: CICS41 Token: 00000028
EB Primary(Asid) Home(Asid) EBSPAWND TCB/SRB -Status-- R14
0624C098 CICS41F (0021) CICS41F (0021) 00000000 006A67D0 Running 00000000
ACE: 0624BE38 Status: T Req: 0003 Allied Chain
CT: 7F2E3030 Short: 7F2C44A0 Long: 7F2C44A0 Vlong: 7F2C4430
Authid: USRT001 Plan: TSTA85 Corrid: PT02XA85 Corrname: CICS41 Token: 00000027
EB Primary(Asid) Home(Asid) EBSPAWND TCB/SRB -Status-- R14
0624BEC8 CICS41F (0021) CICS41F (0021) 00000000 006A6A60 Running 00000000
ACE: 0624BC78 Status: T Req: 0004 Allied Chain
CT: 7F2E1030 Short: 7F2C4580 Long: 7F2C4580 Vlong: 7F2C4510
Authid: USRT001 Plan: TSTA85 Corrid: PT01XA85 Corrname: CICS41 Token: 00000026
EB Primary(Asid) Home(Asid) EBSPAWND TCB/SRB -Status-- R14
0624BD08 CICS41F (0021) CICS41F (0021) 00000000 006A6CF0 Running 861EF578For all storage reports, DSNWDMP displays EDM pool statistics. Those statistics are the same ones that you obtain through DB2 statistics trace reports. The following shows an example report.
==EDM statistics
--------------
Fails due to POOL full: 0
Pages in EDM POOL: 225
REQ for CT sections: 28
Load CT sections from DASD: 3
Pages used for CT: 8
Free pages in free chain: 194
Pages used for DBDs: 18
Pages used for SKCT: 3
Requests for DBD: 24
Loads of DBDS from DASD: 3
Requests for PT sections: 6
Loads of PT sections from DASD: 2
Pages used for PT: 0
Pages used for SKPT: 2
Inserts for dynamic cache: 0
Requests for dynamic cache: 0
Pages used for dynamic cache: 0