Using statistics to select data tables
If your sharing is confined to a single MVS image, you should consider which files have access patterns that make the use of shared data tables beneficial.
If you need to share data between more that one MVS image, you should investigate using RLS mode to share the files.
Figure 1, Figure 2, and Figure 3 show some extracts from a hypothetical set of file statistics for files accessed in non-RLS mode that are used in the following discussion to demonstrate how CICS statistics can aid the selection process.
The statistics are displayed as they would be reported by the CICS offline formatting utility. Requested file statistics are shown, but Interval or End of Day statistics would be equally suitable. The section of File “Performance Information” statistics, which reports use of VSAM strings and buffers, is not shown here.
The numbers shown in the figures are purely for the purposes of illustration, and you should not expect the statistics at your installation to resemble them. Similarly, the configuration of CICS regions and files has been chosen to highlight certain points; it is not suggested that this is a typical or desirable configuration.
Requested Statistics Report Collection Date-Time 12/25/99-11:51:51 Last Reset 09:00:00 Applid CICFOR Jobname SDTGSTF1
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FILES - Resource Information
____________________________
File Data Set Name Data Set RLS DT Time Time Remote Remote Lsrpool
Name Base Data Set Name (If Applicable) Type File Indicator Opened Closed Name Sysid ID
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APPLE CIC01.CICOWN.APPLES K NO 07:44:12 OPEN 1
BANANA CIC01.CICOWN.BANANAS K NO 09:45:08 OPEN 1
ORANGE CIC01.CICOWN.CITRUS K NO 10:51:10 OPEN 2
PEAR CIC01.CICOWN.PEARS K NO 07:30:14 OPEN 3
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Requested Statistics Report Collection Date-Time 12/25/99-11:51:51 Last Reset 09:00:00 Applid CICFOR Jobname SDTGSTF1
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FILES - Requests Information
____________________________
File Get Get Upd Browse Update Add Delete Brws Upd VSAM EXCP Requests RLS req
Name Requests Requests Requests Requests Requests Requests Requests Data Index Timeouts
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APPLE 2317265 1020 0 1019 21 1 0 11503 310 0
BANANA 536452 1674 20344 1674 908 0 0 2651 70 0
ORANGE 2069454 98560 17831 98327 4543 2563 0 8511 481 0
PEAR 45871 65493 6512 65493 30109 362 0 3773 231 0
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*TOTALS* 4969042 166747 44687 166513 35581 2926 0 0
Requested Statistics Report Collection Date-Time 12/25/99-11:51:51 Last Reset 09:00:00 Applid CICFOR Jobname SDTGSTF1
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FILES - Data Table Requests Information
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File Close Read Recs ¬ Adds from Add Adds rejected Adds rejected Rewrite Delete Highest Storage
Name Type Requests in Table Reads Requests - Exit - Table Full Requests Requests Table Size Alloc(K)
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DFHST0223 I There are no data table statistics to report.Requested Statistics Report Collection Date-Time 12/25/99-11:51:38 Last Reset 09:00:00 Applid CICAOR1 Jobname SDTGSTA1
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FILES - Resource Information
____________________________
File Data Set Name Data Set RLS DT Time Time Remote Remote Lsrpool
Name Base Data Set Name (If Applicable) Type File Indicator Opened Closed Name Sysid ID
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APPLE REMOTE CLOSED CLOSED APPLE CIF1 N
BANANA REMOTE CLOSED CLOSED BANANA CIF1 N
ORANGE REMOTE CLOSED CLOSED ORANGE CIF1 N
ZUCCHINI REMOTE CLOSED CLOSED COURGETT CIA2 N
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Requested Statistics Report Collection Date-Time 12/25/99-11:51:38 Last Reset 09:00:00 Applid CICAOR1 Jobname SDTGSTA1
_________________________________________________________________________________________________________________________________
FILES - Requests Information
____________________________
File Get Get Upd Browse Update Add Delete Brws Upd VSAM EXCP Requests RLS req
Name Requests Requests Requests Requests Requests Requests Requests Data Index Timeouts
____________________________________________________________________________________________________
APPLE 1158701 532 0 531 11 1 0 0 0 0
BANANA 305641 0 19067 0 0 0 0 0 0 0
ORANGE 58709 32854 4265 32621 1018 1001 0 0 0 0
ZUCCHINI 78914 0 14765 0 0 0 0 0 0 0
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*TOTALS* 1601965 33386 38097 33152 1029 1002 0 0
Requested Statistics Report Collection Date-Time 12/25/99-11:51:38 Last Reset 09:00:00 Applid CICAOR1 Jobname SDTGSTA1
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FILES - Data Table Requests Information
_______________________________________
File Close Read Recs ¬ Adds from Add Adds rejected Adds rejected Rewrite Delete Highest Storage
Name Type Requests in Table Reads Requests - Exit - Table Full Requests Requests Table Size Alloc(K)
___________________________________________________________________________________________________________________________
DFHST0223 I There are no data table statistics to report.Requested Statistics Report Collection Date-Time 12/25/99-11:49:31 Last Reset 09:00:00 Applid CICAOR2 Jobname SDTGSTA2
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FILES - Resource Information
____________________________
File Data Set Name Data Set RLS DT Time Time Remote Remote Lsrpool
Name Base Data Set Name (If Applicable) Type File Indicator Opened Closed Name Sysid ID
_______________________________________________________________________________________________________________________________
COURGETT CIC02.CICOWN.COURGETT K NO 08:22:15 OPEN 1
LEMON REMOTE NO CLOSED CLOSED ORANGE CIF1 N
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Requested Statistics Report Collection Date-Time 12/25/99-11:49:31 Last Reset 09:00:00 Applid CICAOR2 Jobname SDTGSTA2
_________________________________________________________________________________________________________________________________
FILES - Requests Information
____________________________
File Get Get Upd Browse Update Add Delete Brws Upd VSAM EXCP Requests RLS req
Name Requests Requests Requests Requests Requests Requests Requests Data Index Timeouts
____________________________________________________________________________________________________
COURGETT 78914 27469 14765 27469 336472 0 0 8212 481 0
LEMON 2010745 65706 13566 65706 3525 1562 0 0 0 0
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*TOTALS* 2089659 93175 28331 93175 339997 1562 0 0
Requested Statistics Report Collection Date-Time 12/25/99-11:49:31 Last Reset 09:00:00 Applid CICAOR2 Jobname SDTGSTA2
_________________________________________________________________________________________________________________________________
FILES - Data Table Requests Information
_______________________________________
File Close Read Recs ¬ Adds from Add Adds rejected Adds rejected Rewrite Delete Highest Storage
Name Type Requests in Table Reads Requests - Exit - Table Full Requests Requests Table Size Alloc(K)
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DFHST0223 I There are no data table statistics to report.The examples use a hypothetical configuration of three CICS regions.
Most of the files used by CICS applications are owned by the file-owning
region CICFOR, and the applications mostly run in the application-owning
regions CICAOR1 and CICAOR2. This discussion assumes that each of
the data sets shown in the statistics reports is a VSAM base KSDS
(as indicated by the Data Set Type of K),
so any of them can be defined as data tables.
This section focuses on identifying candidates for defining as CICS-maintained data tables, because the decision to define a user-maintained data table is more likely to come from consideration of particular applications than from a study of file performance in general. Because of this focus, none of the statistics shown is for files accessed in RLS mode, because an RLS-mode data set cannot be the source for a CICS-maintained data table.
The statistics also show you which file names in one region are defined to access file names in another region. The Remote Sysid is the name given on the connection between the two regions. In the examples, the SYSID of CICFOR is CIF2 and that of CICAOR2 is CIA2.