SMF Device Activity by Device Address

The
MICS
BATWDA file provides the capability to analyze the I/O activity of individual devices at the I/S facility. Each observation in the file represents I/O activity for a particular device address. The device class, EXCPs, and device connect time are part of each BATWDA observation. The file is summarized by performance group (PERFGRP), SYSID, and HOUR to allow the study of different workloads at different times.
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The
MICS
BATWDA file provides the capability to analyze the I/O activity of individual devices at the I/S facility. Each observation in the file represents I/O activity for a particular device address. The device class, EXCPs, and device connect time are part of each BATWDA observation. The file is summarized by performance group (PERFGRP), SYSID, and HOUR to allow the study of different workloads at different times.
The BATWDA file accounts for two sets of device classes. One set consists of the true device classes (like DASD and TAPE). The other set consists of "pseudo" device classes (like VIOPAGE and SWAPSSEQ).
The EXCP segments in the raw SMF session, step, and interval records are the source of the BATWDA observations for the true device classes.
MICS
summarizes the EXCP segments by device address as part of the process of building the PGMAxxxx, PGMNxxxx, PGMMXAxx, and PGMMXNxx program level data elements discussed in the following sections - Device Allocations By Device Class and Data Set Allocations By Device Class.
As part of this process,
MICS
checks the SYSID of the step or session record. If the WDA option was specified in prefix.MICS.PARMS(SMFOPS), then observations are produced for each device address that had I/O activity. Device addresses that were allocated but had no I/O activity are not included in the BATWDA file. The following true device classes are accounted for by this EXCP segment processing:
DEVCLASS
Description
TAPE
Cartridge and Round Reel Tape Device
DASD
DASD Device
COMMGEAR
Communications and Teleprocessing Device
CTC
Channel to Channel Adapter
GRAPHICS
Graphics Device (e.g., a local 3278)
UNIT-REC
Unit Record (e.g., a card reader). This is kind of a catch all category containing many unusual devices, such as the 3838 Vector Processor.
VIO
Virtual I/O (DEVADDR always equals "VIO")
The BATWDA file includes a number of "pseudo" device classes produced from other segments of the session, step, and interval SMF records. The amount of activity associated with these pseudo device classes is recorded in the WDAEXCPS data element. Unlike the true device class BATWDA observations, there is no device address to populate the DEVADDR data element. The DEVADDR data element for these pseudo device classes contains an abbreviated description of the pseudo device class. The following pseudo device classes are accounted for in the BATWDA file.
PSEUDO DEVCLASS
PSEUDO DEVADDR
Description
CMNPAGES
CMN
Common Area Page Ins
DEMPAGE
DPG
Non VIO, Non-Swap Page Ins + Non VIO, Non-Swap Page Outs
PAGIN
INS
Non VIO, Non-Swap Page Ins
SWAPIN
SIN
Pages Swapped In
SWAPPAGE
SPG
Pages Swapped In + Pages Swapped Out
SWAPSSEQ
SWP
Address Space Swap Sequences
VIOPAGE
VPG
VIO Page Ins + VIO Page Outs
Each DETAIL BATWDA observation contains the start and end timestamp of the SMF step, session, or interval record that was its source. The device activity is evenly apportioned across each HOUR of the duration. Finally,
MICS
summarizes the BATWDA records to the DAYS timespan. The BATWDA file only exists temporarily at the DETAIL timespan during the
MICS DAILY
update because of the enormous amount of DASD space required.
The method of device activity apportionment over the step, session, or interval is shown in the following example:
Example:
A batch job step runs for 2 hours. The start time is 9:40 and the end time is 11:40.
   |--------|--------------------|---------------|    | 16.67% |        50.00%      |     33.33%    |    | 20 min |        60 min      |     40 min    |    | HOUR 9 |        HOUR 10     |     HOUR 11   |    |--------|--------------------|---------------|    |        |                    |               |  9:40    10:00                 11:00           11:40
MICS
has no way of knowing exactly when each device activity occurred, only that it occurred sometime between the start and end of the step. Therefore, the activity is apportioned over each hour spanned by the step based on the percentage of the total step duration. In the example above, each device address has 16.67% of its activities (ex., EXCPs Connect Time) assigned to HOUR 9, 50% assigned to HOUR 10, and 33.33% assigned to HOUR 11.
It should be clear that as step durations become shorter, the ability to pinpoint the time of device activity increases. Activation of SMF type 30 interval recording significantly improves the accuracy of the device activity data in the BATWDA file.
MICS
management support applications use the BATWDA file to give a complete picture of device and "pseudo" device activity at the I/S facility.