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Memory usage on Tru64 Unix V5.1B

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Danesh Qureshi
Regular Advisor

Memory usage on Tru64 Unix V5.1B

I have a Alpha server ES47 running Tru64 Unix V5.1B.

The server has 8Gb of physical memory.

I have attached the output of "vmstat" with my comments in the attached file.

I would really appreciate if anyone can explain the output of vmstat at each stage when the database was shutdown, the server was rebooted but no database was started and finally when the database was started.

6 REPLIES
Danesh Qureshi
Regular Advisor

Re: Memory usage on Tru64 Unix V5.1B

Sorry please see the output of the second attached file not the first attached file and get back to me.
Rob Leadbeater
Honored Contributor
Solution

Re: Memory usage on Tru64 Unix V5.1B

Hi Danesh,

Could you put some context around your question please... Is there a particular problem you are trying to solve, or do you just want to know what vmstat is showing you ?

If the latter then "man vmstat" would be a good start !

Cheers,

Rob
Danesh Qureshi
Regular Advisor

Re: Memory usage on Tru64 Unix V5.1B

I am trying to understand if the output of vmstat is indicating any memory performance problems on our server. I want to know why the "free" value show 374K and does it indicate a problem.

What fields in vmstat are relevant if my server is having memory problems? The second attached file of vmstat output is the one to look at.
Rob Leadbeater
Honored Contributor

Re: Memory usage on Tru64 Unix V5.1B

Hi Danesh,

It's not 347KB of free memory...

It's 347536 pages of free memory, where each page is 8192 bytes.

By my calculation that's about 2.6GB of free memory.

Cheers,

Rob




Hein van den Heuvel
Honored Contributor

Re: Memory usage on Tru64 Unix V5.1B

As Rob indicates, there is a ton of memory free.

If there is a memory problem, then it is that not enough was given to Oracle and it is just sitting there going to waste instead of being used.

In the first picture, with 'only' 2.5 GB free, the bulk of the rest (580011 pages = 4GB ) was used by UBC, and potentially reall also was free in the it could be reclaimed as needed...

Next a reboot. Nothing has has been put in the UBC just yet, so now 4GB + 2.5G + more = 7+ GB is free.

Finally Oracle is activated and 171291 pages become active (was 7133). That is just 1.4GB or less than 1/5 of the box. A drop in the bucket. Still 3/4 of memory is free for example for Oracle slave tasks as connections are being made (could be from 5 - 20 mb/connection).

So what is the _real_ problem you are trying to address? Only a lack of understanding or a (performance?) user complaint?

hth,
Hein van den Heuvel
HvdH Performance Consulting.
Danesh Qureshi
Regular Advisor

Re: Memory usage on Tru64 Unix V5.1B

Hello Rob/Hein,

It was my lack of understanding of vmstat. I am gratful to you to explain what these values mean in vmstat. I was being asked by our DBA why was there still 2Gb of free pages showing even when the Oracle database was shutdown?