FCX156, DASD Seeks Locations Screen – SEEKLOC

Performance Toolkit Subcommand: SEEKLOC.

The DASD Seeks Locations Screen (FCX156) shows DASD seeks statistics on the frequency with which seeks were made to specific locations for each monitored disk:

Figure 1. Layout of DASD Seeks Locations Screen (FCX156)

 FCX156      CPU nnnn  SER nnnnn  Interval HH:MM:SS - HH:MM:SS    Perf. Monitor
 ____ .                 .    .         .    .     .      .
 <--------- Device ---------->      <------ Seeks -------> <----------- Percent
                     Size Disc                 Mean                Within Perce
      Device Volume    in Time Cach  Pct  Pct Non-0  Total  0<=  10<  20<  30<
 Addr Type   Serial  Cyls msec   ed Read Non0  Dist  Seeks <=10 <=20 <=30 <=40
 >> Mean <<                           32   61   146 174223   29   24    9    6

 0600 3380-K PROFSA  2655 21.2  Yes   13   31   199   4227    6   11   15    0
 0601 3380-K VMPRA1  2655 19.3  Yes   25   38   169    484   35   23    1    3
 0602 3380-K PROFSB  2655 21.6  Yes   13   50   147   5680    1   14   14    7
 0603 3380-K VMPRA3  2655 21.6  Yes   24   48   280  10910   24   31    5    7
 0604 3380-K VMPRA4  2655 13.9  Yes   57   48   177   1613   44    0    1   16
 0605 3380-K VMPRA5  2655 21.4  Yes   19   50   217   5017   11   23   13    6
 0606 3380-K VMPRA6  2655 22.8  Yes   18   49   257   5845    8   17   11    1
 0607 3380-K VMPRA7  2655 20.5  Yes   17   44   217   8071   16    4   12   13
 0608 3380-K ESA111  2655 10.8  No     5    4   814     80    0    0   95    0
 060A 3380-K VMPRAA  2655 21.6  Yes   17   43   213   3133   24   14   22    5
 060B 3380-K VMPRAB  2655 10.7  Yes   54   53   117   6299    3   11    7    4
 060C 3380-K VMPG1N  2655 13.3  No    55   98    92   4206    0    0    0    0
 060D 3380-K VMPG1O  2655 13.4  No    52   99    70   4245    0    0    0    0
 060E 3380-K VMPRAE  2655 21.5  Yes   20   41   206   6888   17    5    5    8
 Select a device for I/O device details
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The sample shows a screen with disks sorted in ascending device number sequence (indicated by the underscore characters above the 'Addr' header), the initial default sequence. Other possible sort sequences are indicated by dots above the corresponding columns, they can be set using the 'SORT' subcommand with the string shown in the lowest line of the column heading as sort argument (see SORT) or by positioning the cursor on the header of the field which is to be sorted and then pressing ENTER.

The information shown is based on MONITOR and I/O domain SAMPLE data and on SEEKS domain EVENT data. The display can be built only when data collection for all these domains is active.

For more detailed seeks data for one specific disk either:

Place the cursor on the Addr field of the disk you are interested in and press ENTER, or
Enter the subcommand 'SEEKDET devno' on the command line

The 'Seeks Analysis Details' screen will then be shown with detailed data for the selected device (see SEEKDET for more information on that performance display).

Field Descriptions:

The following field descriptions apply to both the SEEKLOC and SEEKLLOG devno displays, with the exception of the Addr field which will be replaced by the field Interval End Time on the SEEKLLOG display.

Device:

Addr: Real device number. The first line contains the prefix >> Mean << instead of a device number. It provides averages for all disks for which seeks data were collected.
Device Type: Device type and model of the disk
Volume Serial: The volume serial of the disk. Dots can be shown initially if no I/O sample data have been collected yet for the disk.
Size in Cyls: The number of cylinders available on the disk.
Disc Time msec: The average disconnect time during the interval. Dots will be shown for disks where the disconnect time cannot be calculated, either because we have not yet received two samples which allow calculating a valid delta value, or because there has been no I/O activity during the sample period.

Cached: Indicates whether the disk has profited from the cache during the last sample interval, i.e. whether any read or write hits were recorded. The string Yes will be inserted if hits were found, and No will be inserted otherwise.

Seeks:

Pct Read: Percent of seeks to the disk which were for channel programs containing only READ operations.
Pct Non0: The percentage of seeks that caused a displacement of the access arm of at least 1 cylinder.
Mean Non-0 Dist: The average displacement of the access arm, taking into account only the seeks that caused a nonzero displacement.
Total Seeks: The total number of seeks activity samples recorded for the disk.

Percent of Seek Targets within Percent Range of Cylinders:

The seek targets are grouped into 10 pools, each with a size of approximately 10% of the total number of cylinders. The frequency with which seeks were made to each area is expressed as the percentage of seeks that were targeted to the area, where the seek target headings are as follows:

0<= <=10: For seeks targeted to the lowest range of the disk's cylinders.
10< <=20: For seeks targeted to the next-highest range of the disk's cylinders.
20< <=30: For seeks targeted to the next-highest range of the disk's cylinders.
30< <=40: For seeks targeted to the next-highest range of the disk's cylinders.
40< <=50: For seeks targeted to the next-highest range of the disk's cylinders.
50< <=60: For seeks targeted to the next-highest range of the disk's cylinders.
60< <=70: For seeks targeted to the next-highest range of the disk's cylinders.
70< <=80: For seeks targeted to the next-highest range of the disk's cylinders.
80< <=90: For seeks targeted to the next-highest range of the disk's cylinders.
90<: For seeks targeted to the highest range of the disk's cylinders.

Effect of 'AVERAGE' and 'INTERIM' subcommands: Overall or interim period averages will be shown. Note that overall period averages will also be shown for the 'current' setting.