IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

212 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

When you are capturing data to a file, the nmon tool disconnects from the shell to ensure that it

continues running even if you log out. This means that nmon can appear to crash, but it is still

running in the background until the end of the analysis period.

7.4.3 filemon

The filemon command monitors a trace of file system and I/O system events, and reports

performance statistics for files, virtual memory segments, logical volumes, and physical

volumes. The filemon command is useful to those whose applications are believed to be

disk-bound, and want to know where and why.

The filemon command provides a quick test to determine if there is an I/O problem by

measuring the I/O service times for reads and writes at the disk and logical volume level.

The filemon command resides in /usr/bin and is part of the bos.perf.tools file set, which can

be installed from the AIX base installation media.

filemon syntax

The syntax of the filemon command is as follows:

filemon [-d ][-i Trace_File -n Gennames_File ][-o File ] [ -O Levels ] [-P ] [ -T n ] [

--u ][ --v ]

Flags:

򐂰 -i Trace_File

Reads the I/O trace data from the specified Trace_File, instead of from the real-time trace

process. The filemon report summarizes the I/O activity for the system and period

represented by the trace file. The -n option must also be specified.

򐂰 -n Gennames_File

Specifies a Gennames_File for offline trace processing. This file is created by running the

gennames command and redirecting the output to a file as follows (the -i option must also

be specified): gennames >file.

򐂰 -o File

Writes the I/O activity report to the specified file instead of to the stdout file.

򐂰 -d

Starts the filemon command, but defers tracing until the trcon command has been

executed by the user. By default, tracing is started immediately.

򐂰 -T n

Sets the kernel’s trace buffer size to n bytes. The default size is 32,000 bytes. The buffer

size can be increased to accommodate larger bursts of events (a typical event record size

is 30 bytes).

򐂰 -P

Pins monitor process in memory. The -P flag causes the filemon command's text and data

pages to be pinned in memory for the duration of the monitoring period. This flag can be

used to ensure that the real-time filemon process is not paged out when running in a

memory constrained environment.

򐂰 -v

Prints extra information in the report. The most significant effect of the -v flag is that all

logical files and all segments that were accessed are included in the I/O activity report,

instead of only the 20 most active files and segments.