Memory issues

[Vishal Biyani]

We have a HP-UX box with WebSphere application server and 6 RMI servers deployed. The free memory is generally 10% and free Swap is generaly 15-20%. Even then we get the out of memory errors, in App server as well in RMI (Not at the same time in both though)

Now I need to understand a few basic things
1) How do I find if the memory allocated to a particular process has reached a limit?
2) How do I go about finding the root cause of memory issue
3) I also noticed that the System memory is consistently at 39%, is that a good sign, or it does not matter in overall scenario?
4) Any pointers/docs to memory tuning would be of great help.

I am a novice in memory stuff at OS level, hence any pointers to understand the basics would be of great help. Of course with answers to above queries. Thanks in advance.

[Steven E. Protter · Accepted solution]

Shalom,

1) My memory leak detector does show how much resident memory is assigned to processes.
http://www.hpux.ws/?p=8

2) Identify who is using what and whether or not this grows over time. See reply 1.

3) This is a sign that there probably is no memory leak, but that you may have too much memory allocated overall. Might indicate adding memory to the server is the best course of action.

4)Lots of good docs

http://docs.hp.com/en/1218/mem_mgt.html

http://docs.hp.com/en/B3920-90091/ch04s03.html

Pick your fun above.

SEP

[Bill Hassell]

> we get the out of memory errors

This message never means that the system does not have enough memory. HP-UX is a virtual memory system and after your processes use 100% of memory, it will still run without problems by using swap space. This error is very often related to old 32 bit applications that have severe restrictions on the amount of local and shared memory. The programs can be recompiled with options to allow for larger local and shared memory segments. Shared memory for 32 bit programs can easily become fragmented, especially when processes are killed with -9.

For the questions:

1. There is no way to know what the program limits are without reading the code and looking at the program's memory mapping options. When a process reports out of memory, you need to go to the programmer and ask what the error means. Whether you have 2 GB or RAM or 128 GB of RAM, a 32 bit process will run out of memory due to mapping restrictions. You can't change this without help from the programmer.

2. The programmer will tell you.

3. 39% is way out of line for a 128 GB system, but perfectly normal for a 2 GB system. Kernel parameters that are far too large can increase the kernel's size but it doesn't really matter until you fix the processes. You have plenty of memory as long as swap space isn't completely used. On the other hand, 15-20% free swap means that there is likely significant paging going on. Use vmstat to see the po (page out rate). 2 digits is a concern, 3 digits means you are very short of RAM and need to double or triple the amount to improve performance.

[Gokul Chandola]

Hi,
There should be the option for memory setting and Kernal setting for WebSpare in Application specification.
What Karnel setting should be, these setting are generally defined in Apllication Technical requirement/parameter.

Regards,
Gokul Chandola