VMS cluster + ORACLE + ERP

[Rob Crooks]

I am contemplating introducing an ERP to an OpenVMS cluster of 2 DS20s and would like to gauge what the result would be.

The plan is to run about 150 sessions of ORACLE 9i on one node, and 150 session of the ERP application on the other. As the ERP is not cluster aware, I will have to fail over the ERP app manually along with the ORACLE instance if I lose communication between the nodes or one node completely (I have 2 computer rooms, 1 node in each). I have only 2 CPU licenses for ORACLE, so I can't run RAC (and it is Enterprise so I can't really afford another either).

The ERP vendor says that I sould expect about 30Mb per session for both applications.

My question is

If I run both apps on one node due to a disaster, and the DS20 has only 4Gb, what can I reasonably expect if my db uses 4.5Gb and the ERP uses 4.5Gb?

As I write this, my current system load is 2.3Gb just with some in-house order entry 4GL screens running.

I know this sounds like a loaded question, but even from what I have seen of everyone extolling the virtues of VMS, I can't see how
anything can be expected to run of these applications if they demand 3 times the available physical memory.

I would appreciate hearing any information or opinion, ancedotal or not, on what I should expect.

Thanks

[Wim Van den Wyngaert]

Should be no problem. But make sure your pagefile is larger than what you need.
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=899371

Also : how many processes are concurrently active ?

Wim

[Wim Van den Wyngaert]

You could set wsextent to 1/3rd of the memory the process needs and see how it reacts. If there are not many pagefaults (soft faults in the test but those will be hard faults when you run everything on 1 node), it should be no problem when most processes run concurrently.

Of course only if you're allowed to play ...

BTW : I monitor my cluster nodes for 50% of their resources. So I now it will work when I put everything on 1 node (number of telnet sessions, pagefile usage, interactive limit, ...).

Wim

[Rob Crooks]

If I look right now, there are about 115 active processes.

I understand about your 50% rule, but for me in this case I can only see that I am asking for 100%+ of resources for each node.

Are you saying that I will see no difference in the response of the DB or the ERP app if I load one node down like this?

[Wim Van den Wyngaert]

It all depends on how many memory you are really using.
E.g. if your process is actively using 10% of the memory it has consumed, you should have no problem. If your program is doing a scan of the 30 MB all the time, you have a problem. Unless that memory is shared.

For the db server its the same. You assigned a lot of memory to it. Is it using all of it ? If you do a join and the data doesn't fit in memory and indexes are not present, it can take A LOT longer.

Any way, you will have to decide on a strategy of how VMS must react when physical memory is exhausted (decrease working sets/swap out processes).

I would certainly test it (on a quiet day).

Wim

[Wim Van den Wyngaert]

Active processes : check how many processes did an IO or used the cpu during e.g. 1 minute/1 hour to get an idea.

Wim

[Jan van den Ende]

Robert,

MUCH hinges on how much you can INSTALL shared.
Then again, that means much hinges on how much your vendor understands of the workings of VMS, and since the app is not even cluster-aware, I do not have high hopes there.
Is it possible to have the app for test for, let's say, a month?
To measure = to know, but to gamble, more often than not, = to loose, one way or the other.
Much depends on the REAL use of those sessions: users that are logged in, but not actively using it are dealt with quite effectively by VMS, but simultanious real activity any system can do only so much.

hth

Proost.

Have one one me.

jpe

[Rob Crooks]

Thanks to both of you. I have enough information now to approach this intelligently. From the discussion I take it that VMS is flexible, but like any system, sometimes too much is too much.

So, like seems to be the best advise, is to be conservative.


Much appreciated. :)

[Jan van den Ende]

Robert,

thanks for your points assignment, but I think you should have given Wim some also!
(And from your thanks to both, I assume you really think so also).

Proost.

Have one on me.

jpe