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.rm
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.