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I/O Performance and Monitoring Tools 133
same view as cache reports for each LCU: and second, between all LCUs to get
the whole storage server view. Some tools, such as IXFP, offer consolidated data.
In the case study activities, there is only one active LPAR, so only LCU level
consolidation is done.
11.2.2.2 RMF Reporting at Storage Group Level
The RMF DEVICE report, when edited at the Storage Group level, shows the
Storage Group’s overall performance from which it is easy to deduce required
parallelism. This example focuses only on required fields from DEVICE report at
the Storage Group level for a query-intensive activity:
• DEVICE ACTIVITY RATE: 1,042.261
• AVG CONN TIME: 22.3
The required path occupancy (see 11.2.1.2, “Direct Access Device Activity
Report” on page 128) for this workload is:
( (1,042.261 x 22.3 ) / 1000 ) x 100 =2,324 %
Therefore, there is a minimal path demand of 24 (23+1). It is wise to allocate such
a workload over at least 32 paths, so this Storage Group should be spread over
four RVAs with a multiple of eight volumes on each. When there are performance
issues, and consolidated channel path performance data shows normal values,
as the origin of those is in throughput demand flow (MB/sec), check for high
disconnect and/or pending times.
11.2.2.3 Tools Providing More In-Depth Analysis than RMF
When RMF reports show some performance issues that require more in-depth
analysis, a generalized trace facility (GTF) of channel command words (CCWs)
should be used. PLease refer to
OS/390 V2 R6.0 MVS Diagnosis: Tools and
Service Aids
, SY28-1085, on how to customize the CCW trace. This trace is
time-stamped, so storage specialists can control the channel programs issued
and analyze their behavior. Some capacity planning information can only be
derived at the trace level, in particular bandwidth information, such as number of
MB/sec in read and/or in write activities. Such information requires knowledge of
the data transmitted by each command. However, for the RVA, an IXFP report
edits the global bandwidth, with reads and writes mixed. IXFP calls some internal
RVA facilities that dynamically maintain these statistics.
11.2.2.4 Spreadsheet Tools for RMF Analyzis
Two tools, RMF spreadsheet converter (RMF2SC) and RMF spreadsheet
reporter (RMFPP), allow automatic data capture from standard RMF Monitor III
printouts to most common spreadsheet tools. For RMFPP, the printouts should
have been previously saved in EBCDIC format (preferably in fixed mode to allow
high quality transmission) in the host before they are downloaded to a PC. These
RMF tools are described in Part 6 of the
OS/390 V2 R6.0 RMF User's Guide,
SC28-1949.
RMF2SC takes output from RMF and converts it to spreadsheet formats.
Working with RMF spreadsheets involves three steps:
1. Using RMF to generate the appropriate reports. The result can be in a data
set, which you can download to the PC and process as a host data set or
on the screen.