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Viewing page set considerations (I/O GBP-DEP)

Data sharing means that some or all of the DB2 tables can be accessed concurrently from all members of the group. Native DB2 tools provide only a limited understanding of the impact of data sharing. This section illustrates the power of SSI to give you a more in-depth understanding of the impact.

To view page set considerations

One of the key tuning areas in DB2 is I/O analysis. But looking at I/O for shared page sets or volumes from one DB2 member at a time does not give a complete picture.

  1. On EZDSSI, hyperlink on Data Sharing Menu.

  2. On EZDSHAR, select Volume I/Os (SSI).A view of total I/O per volume from all members (PSVOLSSI) is displayed.

    10MAR2011 15:46:52 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
    COMMAND  ===>                                                 SCROLL ===> CSR
    CURR WIN ===> 1        ALT WIN ===>
    >W1 =PSVOLSSI=========(DBGHC====*=======)10MAR2011==15:46:37====MVDB2===D====13
                Sync   I/O Sync Max  Sync Avg                 Async   I/O    Async
     Volume     I/Os    %  I/O Wait  I/O Wait 0....20...40     I/Os    %     Pages
     BAB309        6   0.4       31        17 *****               2   0.0        2
     BAB310      309  19.9      354        23 *******            31   0.5      104
     BAB311        3   0.2       38        20 ******              0   0.0        0
     BAB312     1120  72.3    10322        32 **********       5732  91.8    44287
     BAB314        8   0.5       98        29 *********           0   0.0        0
     BAB317       36   2.3      176        27 ********            0   0.0        0
     BAB318        5   0.3       27        16 *****              0   0.0        0
     BAB322       12   0.8       38        14 ****              449   7.2     3535
     BAB325        9   0.6       52        16 *****               0   0.0        0
     BAB330        8   0.5      104        25 ********            0   0.0        0
     BAB331        8   0.5       30        15 ****               19   0.3      143
     BAB332       15   1.0       30        10 ***                 8   0.1       61
     TSG314       11   0.7       31        16 *****               3   0.0       14

  3. Select one of the volumes to see how many page sets are being accessed on that volume from each DB2 (PSVOLSZ).

    10MAR2011 15:50:40 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
    COMMAND  ===>                                                 SCROLL ===> CSR
    CURR WIN ===> 1        ALT WIN ===>
    >W1 =PSVOLSZ==========(DBGHC====*=======)10MAR2011==15:50:39====MVDB2====D====2
             DB2       Nr.     Sync   I/O Sync Max  Sync Avg                Async
     Volume Target     PSs     I/Os    %  I/O Wait  I/O Wait 0...20...40     I/Os
     BAB312 DB1HC       13       69   4.1    10322       188 **********+        0
     BAB312 DB2HC       17     1102  66.1     1796        22 ******          5732
  4. Hyperlink on Nr. PSs for one of the members to see a list of each page set (PSVOLPS) with I/O data for that member only.
  5. Press F3 to return to PSVOLSZ.
  6. Hyperlink on Volume for the same member.Now you see a list of all page sets on that volume (PSVOLPSZ) and how many members access each. The I/O data here shows totals for the group.

  7. Hyperlink on Volume once again.Now the list shows each page set with the I/O data broken down per member (PSVOLPS).

    10MAR2011 15:53:44 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
    COMMAND  ===>                                                 SCROLL ===> CSR
    CURR WIN ===> 1        ALT WIN ===>
    >W1 =PSVOLPS==========(DBGHC====*=======)10MAR2011==15:53:33====MVDB2===D====30
            ------Page Set-------  DB2         Sync  Sync Max  Sync Avg
     Volume Database Object   Prt Target       I/Os  I/O Wait  I/O Wait 0...20..40
     BAB312 DSNDB01  DSNLLX02 001 DB1HC           4        29        12 *
     BAB312 DSNDB01  DSNLLX02 001 DB2HC          11        28        24 **
     BAB312 DSNDB01  DSNSPT01 001 DB1HC           5        28        17 **
     BAB312 DSNDB01  DSNSPT01 001 DB2HC           8        29        15 **
     BAB312 DSNDB01  SPT01    001 DB1HC           3        36        27 ***
     BAB312 DSNDB01  SPT01    001 DB2HC          21        40        13 *
     BAB312 DSNDB06  DSNADH01 001 DB1HC           3        43        17 **
     BAB312 DSNDB06  DSNADH01 001 DB2HC          23       221        37 ****
     BAB312 DSNDB06  DSNATX01 001 DB2HC          13       145        30 ***
     BAB312 DSNDB06  DSNATX02 001 DB1HC          12       155        40 ****
     BAB312 DSNDB06  DSNATX02 001 DB2HC         139        98        17 **
  8. Press F3 until you return to EZDSSI.
  9. Select the Data Sharing Wizard.
  10. View the options under Page Set Considerations?.The options under Page Set Considerations? provide another way to access the volume I/O data that you viewed previously.

    1. Select Check GBP-DEP by Member.The WZDSDEP view shows the level of sharing.

      10MAR2011 16:01:31 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
      COMMAND  ===>                                                 SCROLL ===> CSR
      CURR WIN ===> 1        ALT WIN ===>
       W1 =WZDSDEP==========(DBGHC====*=======)10MAR2011==16:01:30====MVDB2====D====2
       DB2      MVS         GBP   Local  Remote Log Recs  Ckpts To  Mins. To   Delete
       Target   System      DEP R/W Int R/W Int  To Ckpt PCLOSE(N) PCLOSE(T)    Names
       DB1HC    SYSC          4       4       4    50000         5        10        0
       DB2HC    SYSC          4       4       3    50000         5        10        8

      This view summarizes how many GBP-dependent page sets are in the group per DB2 member. The view also includes the key ZPARM values that affect how long a page set remains in this status.

    2. Move the cursor to the column header, Mins to PCLOSE(T), and press F1 to get field Help on this value.Many field Help panels, like this one, contain tuning tips in addition to the field definition.

      10MAR2011 16:01:31 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
      COMMAND  ===>                                                 SCROLL ===> CSR
      CURR WIN ===> 1        ALT WIN ===>
       W1 =WZDSDEP==========(DBGHC====*=======)10MAR2011==16:01:30====MVDB2====D====2
       DB2      MVS         GBP   Local  Remote Log Recs  Ckpts To  Mins. To   Delete
       Target   System      DEP R/W Int R/W Int  To Ckpt PCLOSE(N) PCLOSE(T)    Names
       DB1HC    SYSC
       DB2HC    SYSC             Help       Pseudo-Close Timer Parameter       Help
                                 Command ==>                        Scroll ==> CSR
                                 --------------------------------------------------
                                 This value lists the amount of time, in minutes,
                                 that must elapse before a data set can be a
                                 candidate for pseudo-close (QWP1TMR).
                                 ZPARM name: PCLOSET in DSN6SPRM
                                 Tuning Tip: The PCLOSEN and PCLOSET parameters are
                                             associated with pseudo-close. PCLOSEN
                                             defaults to 5 system checkpoints and
                                             PCLOSET defaults to 10 minutes. There
                                             is a trade off in setting these
                                             parameters. If these values are set
                                             too high, data sets may remain
                                             GBP-dependent for longer than
                                             necessary and incur unnecessary
                                             performance overhead. If these values
    3. Press F3 until you return to the Data Sharing Wizard (WZDSHAR).

  11. Under Page Set Considerations?, select Check GBP-DEP by GBP/PS.The Buffer pool page set GBP-DEP summary (PSBPGBPZ) is displayed.

    10MAR2011 16:18:16 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
    COMMAND  ===>                                                 SCROLL ===> CSR
    CURR WIN ===> 1        ALT WIN ===>
    >W1 =PSBPGBPZ=========(DBGHC====*=======)10MAR2011==16:18:15====MVDB2====D====2
     Bfrpl   DB2       Nr.    GBP        Local         Remote       VP        VP
      ID    Target     PSs Dependent  R/W Interest  R/W Interest  Current  Changed
     BP00   DB1HC       56         2             1             1      200        0
     BP00   DB2HC       72         2             1             1       88        1

    This view summarizes the same data, also for the whole group, but now organizes it per group buffer pool and member.

    1. Select one pool (under Bfrpl ID) to see a list of all open page sets in that pool for all targets.
    2. Press F3 to return to PSBPGBPZ.

    3. Hyperlink on the GBP Dependent column to list only the GBP-dependent page sets in that pool (PSGBP).

      10MAR2011 16:19:22 --------MainView WINDOW INTERFACE (V6.0.00) ---------------
      COMMAND  ===>                                                 SCROLL ===> CSR
      CURR WIN ===> 1        ALT WIN ===>
      >W1 =PSBPGBPZ=PSGBP===(DBGHC====*=======)10MAR2011==16:18:15====MVDB2====D====4
       ------Page Set-------  DB2         No. GBP Local    Remote      VP       VP
       Database Object   Prt Target   Ty Usrs Dep Interest Interest  Current  Changed
       DSN8D51A DSN8S51E 001 DB1HC    PS    0  Y  R/O      R/W             1        0
       DSN8D51A DSN8S51E 001 DB2HC    PS    0  Y  R/W      R/O             0        0
       DSN8D51A DSN8S51P 001 DB1HC    TS    0  Y  R/W      R/O             2        0
       DSN8D51A DSN8S51P 001 DB2HC    TS    0  Y  R/O      R/W             0        0

      You can see which members are GBP-dependent, which members have Read/Write Interest, and how many pages from that page set are cached in each member’s local buffer pool.

  12. Press F3 until you return to the Data Sharing Wizard (WZDSHAR).

Related topic

Monitoring-a-DB2-data-sharing-group

 

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