How to Read SEGSTATS.TXT

  • 3529262
  • 23-Jan-2007
  • 16-Mar-2012

Environment

SEG.NLM 2.00.16
The SEGSTATS.TXT can be created using the / (forward slash) key on any SEG.NLM screen by hitting the key, then arrowing over to "INFO" on the menu, then down to "Write SEGSTATS.TXT. The file can be found in SYS:\SYSTEM.

Situation

How to read a SEGSTATS.TXT File

Resolution

Download seg.nlm 2.00.16 here seg.nlm

Since the release of post-SP5 SERVER.EXE's, memory tuning has defaulted to normal (ie, the server tunes itself) and all known memory leaks/fragmentation issues have been resolved.

Additional Information

The picture of the 5 different address spaces in dashes represent how the memory is divided up in the server. We will focus only on the 3 main pools: Virtual Memory Cache Pool (VM Pool), File System Cache Pool (FS Pool), User Address Space (UAS).

Virtual Memory Cache Pool and the File System Cache Pool:Look at the size of both pools. In most cases, the VM Pool should be bigger. 95% of NLM's allocate memory from the VM Pool. So this normally should be the biggest pool of the 3 main pools.

Total LP Pages:If this number is > 0, it means that the VM Pool is borrowing cache from the FS Pool. This is a condition we want to avoid, so as above, making the VM Pool the largest will help to avoid this condition.

Largest Segment:This number in the VM Pool will not be available on a 6.0 server. This represents the largest contiguous block of cache that each pool has. It is not necessarily the entire amount of free space that this pool has, as will be explained a little lower in this paragraph. The bigger the number, the better it is for memory requests. If you notice that this segment size is dropping down over the period of a few days, weeks, etc, and not flat-lining, this a definite indication of memory being used on the server, and possible fragmentation. If this dropping number is in the VM Pool, consider increasing the VM Pool size. If this dropping number is in the FS Pool, consider hard setting NSS for it's cache settings. However, there is one caveat to this number. There is a line that the VM Cache Pool tracks (not a line currently viewable in SEG.NLM) called the "Lowest Available Logical Kernel Page" which will move down if an NLM needs more memory from the VM Cache Pool, and the memory request is larger than the currently available largest segment. Basically, this line lives in the VM Cache Pool, somewhere above the File Cache Maximum Size line. If the VM Cache Pool cannot grant a request for memory, and if it can move this line down within it's own pool, it will do so, and then grant the memory request from the VM Cache. When this line drops below the File Cache Maximum Size limit (which is the barrier between the VM and FS Cache Pools), and the VM Cache Pool still cannot grant the memory request, this is where borrowing occurs from the File System Cache Pool. A representative number for this line in the VM Cache Pool will be available in an updated version of SEG.NLM.

High Water Mark:This number represents the highest amount of used cache that the NLM's of that particular pool have reached. Theoretically, this should be less than the total size of the pool. If the server has been up for a while and this number does not grow and there is a large discrepancy between the size of the pool and the High Water Mark, you may want to consider giving this memory to another pool. For example, if you had a 6.5 SP3 server that has been up and running for 2 weeks, and the size of the UAS is 992 MB, while the High Water Mark for that pool is only at 575 Mb, you can give a good chunk of that 417 MB of unused cache to the VM Pool. This is accomplished using the -u parameter with SERVER.EXE.NOTE: The only 2 pools that you will want to take memory from 99% of the time is the User Address Space and FS Cache Pool.

Top 6 Memory Consuming NLMs:This is helpful when we see that an NLM or two is out of control in using memory. If NSS, then we can hard set how much cache it is given. If DS.NLM, same thing. If either of these NLM's are large, check to see if there are NSS or DS Configuration files. If they do not exist, then See KB 10091980 for both of these recommendations.

Total Fragmented:This number is representative of the"FS Cache Fragmented" and "LS Cache Fragmented" numbers combined. Basically, how much memory from both pools is fragmented. If this number is growing, determine which pool is contributing to this number the most. The "LS Cache Fragmented" number is coming from the VM Pool. If both numbers are, then it needs to be determined who is doing it. You can hard set the NSS cache, as I mentioned above. That should stop the FS Cache Fragmented number from increasing. If NSS is hard set, and this is increasing, check to see if "Total LP Pages" is counting upwards.


The FILE CACHE MAXIMUM SIZE will move the line between the FS Pool and the VM Pool up or down, depending on what you set the number to. The server - u parameter will move the line between the UAS and the VM Pool up or down, depending on what you set the number to. The The FILE CACHE MAXIMUM SIZE parameter, and the server -u setting in the AUTOEXEC.BAT are discussed more in depth in KB 10091980..
NOTE:Below are 2 methods for setting up the server to automatically record and store multiple copies of SEGSTATS.TXT on regular intervals of 15 minutes.

IMPROVED METHOD (6.x servers only):

With NetWare 6.x (due to conditional scripting commands (%if, %env, etc)) you can setup a more comprehensive method to record SEGSTATS. This method allows a more "hands off" approach when it comes to monitoring the system. Feel free to use either method on 6.x. Use the OLD METHOD listed below for 5.x servers. Please follow these steps:

1. Create a SAVESEG.NCF file and insert the following information. Place this NCF file in your SYS:\SYSTEM directory:

seg writestats
%if !loaded tbx then cmd tbx /nl
%if loaded tbx then cmd cp sys:system\segstats.txt sys:system\segstat\[env %hour]-[env %minute].txt

2. Edit your SYS:\ETC\CRONTAB file. Insert the following information:

0,15,30,45 * * * * SAVESEG.NCF

3. Edit your SYS:\SYSTEM\AUTOEXEC.NCF file. Add the following lines at the end of the file:

LOAD SEG
LOAD CRON

This will create SEGSTAT.TXT at 15 minute intervals and backup them up to SYSTEM\SEGSTAT\(CurrentTime).txt. Backups will be overwritten starting at midnight the next day, keeping 24 hours worth of statistics available and eliminating the need to manually load CRON after startup.

If you need more history, use other combinations of builtin environment variables (type %env at the system console to see what's available). For example, the following will keep backups for a week before starting to overwrite (the weekday variable is 0=Sunday, 1=Monday, etc)

%if loaded toolbox then cmd cp sys:system\segstats.txt sys:system\segstat\[env %weekday]_[env %hour]-[env %minute].txt

This information was obtained from https://www.novell.com/coolsolutions/tip/17033.html

OLD METHOD (and for 5.x):

(NOTE: This method will only retain 2 copies) If you would like to have the system continually write SEGSTATS.TXT for you every 15 minutes (so if the server crashes you have a SEGSTATS written within 15 minutes of the crash) then follow these steps:


1. In your SYS:\ETC\CRONTAB file add the following lines:

0,15,30,45 * * * * seg writestats
0,15,30,45 * * * * load tbx.nlm
1,16,31,46 * * * * cp sys:\system\segstats.txt sys:\system\segstats.old
2,17,32,47 * * * * unload tbx.nlm


2. Load SEG at the server console and let it run (if it does not continually run, then this wont work)

3. Load CRON

4. DO NOT LOAD CRON AUTOMATICALLY ON BOOTUP FOR THIS METHOD. If the server crashes, then we have the needed files, but if you automatically load CRON on bootup it will overwrite the SEGSTATS.* files that will be of most use. Just load the NLM manually for now. Loading SEG.NLM automatically on bootup is fine as it just appends to the existing file (SEG.CSV).

Essentially, this will write a SEGSTATS.TXT file every 15 minutes and will also keep 1 backup file, SEGSTATS.OLD, that will be 15 minutes older than the latest SEGSTATS.TXT. SEG.CSV is constantly being written to while SEG.NLM is running. These files are all stored in the SYS:\SYSTEM directory. YOU WILL NOTICE TOOLBOX LOADING AND UNLOADING WHILE THIS CRONJOB IS RUNNING. Toolbox (tbx.nlm) is used to copy SEGSTATS.TXT to .OLD every 15 minutes so there is a backup copy.

Formerly known as TID# 10097396

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