Filter
Top Products
I/O Performance and Monitoring Tools 125
Most of the RMF reports are issued either at the central processor complex
(CPC) level for a global view, or at the logical partition (LPAR) level for each MVS
image view.
The following two processes can be used to extract relevant data from the
various RMF reports:
1. Determine which fields, from which reports, are useful for a DB2 performance
analyst. Most of this data is also required by IBM storage specialists for disk
evaluation.
2. Determine how to aggregate and handle the raw data to get
resource level
occupancy information.
11.2.1 RMF Report Analysis
The data required for analyzing DB2 disk activity comes from four RMF reports
which are produced by RMF Monitor I or Monitor III reporting (see Chapter 5,
"Long-Term Overview Reporting with the Postprocessor
" in the OS/390 RMF
Report Analysis,
SC28-1950). The two main RMF reports are cache and device:
• Cache Subsystem Activity - Cache Reports
The cache reports provide cache statistics on an LCU level referring to the
LCU by its subsystem identifier (SSID). The accounting methodology for the
number of I/Os is different from the methodology used for the device report.
So, use a percentage instead of a value when you want to establish
correlations between the two reports.
• Direct Access Device Activity - Device Report
The device report triggers path analysis through I/O queuing and provides
information for all disk devices per LCU (referred by LCU number). The
easiest way to associate this device information with complementary
information in the cache reports is to use
device number ranges. The device
report is also an anchor point for measuring path activity.
To obtain path activity information, you can use use:
1. I/O Queuing Activity - IOQ Report
The IOQ report determines, for each LCU, the channel path identifiers
(IDs) used. It also allows analysis of potential pending time issues due to
channel subsystem.
2. Channel Path Activity - CHAN Report
The CHAN report gives channel link effective activity.
11.2.1.1 Cache Subsystem Activity Reports
RMF Monitor I gathers data for cache subsystem activity reports in SMF record
type 74.5 as a default option. To produce the reports, specify:
REPORTS ( CACHE ( SUBSYS ) )
Note: The SUMMARY and DEVICE options must not be used.