Performance data from nmon
Nmon is a popular tool for monitoring of AIX and Linux. It can be used to collect performance data into a single ascii file with lots of very useful information on system variables. The file can be later managed to create reports or to perform performance analysis.
In order to collect data, the basic nmon syntax is the following (use nmon -help for details):
nmon -f -s <sample time in seconds> -c <number of samples>
The tool creates in the current directory a file named <hostname>_YYYYMMDD_HHMM.nmon that contains system information and performance data collected. Using the -F flag a specific filename can be used.
If you only have available a sorted nmon output, use the unsort-nmon script
to format the file for pGraph (Usage: unsort-nmon <source> <dest>).
A typical data collection lasts for 24 hours with a sampling time that depends on the type of event that the user wants to identify. The shorter the time the bigger is the file created and a more fine grained analysis can be made.
Since pGraph has no file size limitation and it enables user to have a quick look to the entire period and then zoom to a specific time period, it is suggested to collect data with a small sampling time. The real limitation can be the space available on the system for file creation. During benchmarks a 5 seconds is usual, for production systems a range from 60 seconds to 900 seconds (15 minutes) can be more appropriate.
pGraph can read in either interactive-mode and in batch mode a single file o multiple files produced by nmon.
Single file
When pGraph reads a single nmon file, it provides the GUI shown by the following figure:
The same set of information is provided in batch mode.
Multiple files from the same host
Monitoring normally lasts for several days if it is not continuous. It is common to produce multiple nmon files, each related to a single day. While it is possible to handle each file by itself, pGraph is capable to manage multiple files as a whole.
Put all nmon files that require analysis in the same directory and use pGraph to read the directory with the menu or flag that states single host, multiple files. pGraph will internally concatenate the data and handle the set of files exactly as if a single file was provided. There is no requirement on the file names.
Multiple files from multiple hosts
It is common to analyze multiple systems at a time, especially when LPARs are involved. In this case pGraph focuses on CPU performance data related to multiple hosts where each file represents a single host.
pGraph extracts CPU data from each file and creates the following performance graphs:
- Average CPU statistics (User, System, Wait, Idle) for each host.
- Physical CPU usage for each host, if it is a micro partition.
- The sum of physical CPU usage of all micro partitions, if present.
- The shared free pool size, if this information is provided by at least one file and if all files are related to hosts belonging the the same physical system.
