memory issue

[Fairdaus]

actually our server memory now is 4 GB for appserver and dbserver.it mean 8 GB.

we have another server and the memory 2GB only.

The system running application using 2 server now is ok but when one server down the system very slow.

our company in process to upgrade the memory.

I just want to know how much we must to upgrade memory for our system application. It mean when one server down the another server can handle the system.

information
server Hp-ux b.11.11
64 bit
oracle 10g database
oracle application 10g 10.1.2.2.0
the system application using oracle forms and report (pdf)

[A. Clay Stephenson]

There is no way to answer your question except "it depends". How big are your SGA's? Are you running cooked files for Oracle or raw devices? If raw, you can greatly reduce your buffer cache (down to 100MiB or so) and gain some space. What are your current settings of dbc_min_pct, dbs_max_pct, and bufpages? How many separate forms instances will you be running? What is the incremental memory footprint of each form instance?

Essentially you want to add enough physical memory to your system so that the page-out rate using vmstat or Glance is no more than about 15 or so and 0 is ideal. You could also choose to reduce the number of processes or the size of the SGA's. Reducing buffer cache and SGA size is a much better alternative to swapping because swapping (paging out) imposes at least a 100x performance penalty.

If you are reading into my response that you haven't even begun to ask the right questions then you are reading correctly.

[Bill Hassell]

This is an impossible question to answer because your database administrator controls the majority of memory, called SGA for Oracle. If your DBA configured 1Gb for your 2Gb system, then 50% of your RAM is used by Oracle shared memory. With all the other programs and the kernel buffer cache taking the more RAM than you have, you are very likely paging very heavily. This reduces performance by as much as 10:1 to 50:1.i

Now your DBA could reduce the SGA to perhaps 500Mb but now the database will run very slowly because there isn't much room to buffer disk requests.

So if you cannot upgrade memory to at least 8Gb total, you'll have to get used to very, very slow performance. You could try putting in another 2Gb for a total of 4Gb but if you are paging out with 4Gb, it still is not enough RAM. You can see your paging rate with vmstat -- look at the po column.