Memory Usage

[Nelson Laracuente]

We have an RX4640 running HP-UX 11iv2. We use it as a production machine. It originally had 8GB of RAM and we added 16GB additional to a total of 24GB. We did this because we were migrating accounts to that machine and increasing the amount of users. This caused for memory use to spike usage in the high 90%. Once we added the memory the usage went down to 80%. However, we were migrating more accounts and users. Today some users complained of performance. I indicated to administration that as these migrations happened that the addressing of additional memory would have to be sooner than later. We are at that point again in less than two months. I believe this machine needs more memory to handle the users, databases and accounts. Today we were are 98% memory use with 239 users. I believe this explains some of the behavior. The machine does have 4 1.6GHz processors. But when you have eloquence and our proprietary software hogging most of the memory usage, it really paints the picture of the actual solution here. I have been asked to seek a way to fine tune the memory usage. I have been looking at PRM and its use. I will further explore that avenue. Does anyone have any suggestions or advice? Thank you.

[A. Clay Stephenson · Accepted solution]

The first thing to look at is dbc_max_pct; it may still be at the default value of 50% when with 24GiB you probably should be no more than 5-10% and that is very generous. The next thing you should be is examine your application and databases for large shared memory use and perhaps that can be scaled back. In any event, very high fractions of total memory use is not bad as long as you are not seeing significant pageout rates. If you are seeing pageouts then you should immediately start tuning applications and databases to reduce their memory footprint because the performance impact from swapping will be at least 100x that of having to go to disk more often for data that are not cached.

[Nelson Laracuente]

Thank you. We are looking at HP Process Resource Manager and Workload Manager as options to tune CPU and Memory. We have modified the default setting. Thank you for your help.

[Nelson Laracuente]

Closing as we are looking at PRM & WLM to perform capping.