System Memory

[Michael Ernstoff]

I have noticed that system memory on my 64 bit 11.11 systems is typically around 1Gb, whereas on my 64 bit 11.00 systems is around 250Mb.
These figures are being taken using Glance.

Do these figures seem reasonable/typical?

A "typical" 11.11 system is an rp7410 with 4 CPUs and 8Gb physical memory.
Oracle is running and kernel parameters include
dbc_max_pct 20
maxdsiz 0X10000000
maxssiz 0X02000000
maxssiz_64bit 0X02000000
maxtsiz 0X10000000
nstrpty 60
semmni 2048
semmns 5120
shmmax 0XFFFFFFFF
shmmni 1024
shmseg 1024

[Michael Tully]

For starters the buffer cache should only need to be between 300-500Mb no more. Depending on the applications/datbases being used it is a little hard to give an indication on the rest. So with 8Gb RAM the dbc_max_pct should be 5%

[Bill Hassell]

maxdsiz is 0x10000000 = 268 megs which is the maximum data area for 32bit programs and should be fine for Oracle (local data doesn't grow that much in individual programs). However, some middleware or other programs may require more RAM and since this is a runaway-program fence, it might artificially limit the amount of RAM for specialized programs. You can leave it as is or increase it to 900 megs for future programs that may need a lot of RAM.

maxssiz is 0x02000000 = 33 megs. The stack on a program is typically used for parameter passing inside a program between functions and subroutines. The vast majority of programs are well below the default (0x800000 or 8megs) limit. It doesn't hurt anything to have it larger since it is only a protection fence.

maxdsiz_64 is 0x02000000 = 33 megs, and that is definitely a problem. maxdsiz_64 is a fence for 64bit programs which can address terabytes of data if needed. However, if maxdsiz_64 is less than maxdsiz, then maxdsiz's fence is lowered to maxdsiz_64. Change maxdsiz_64 to at least 0x10000000, but to save another reboot, I would probably set it to 0x80000000 (actually, I prefer to use decimal so in SAM, set it to 2000000000 which is 2Gb).

maxtsiz is 0x10000000 = 268 megs which is far too high. This is the size of an executable prorgram's instruction set (the program's text area). If you use the size command on a typical program, you'll see just a few Kb. The default is 0x4000000 or 64megs, more than enough for 99% of programs. You can also get a rough estimate of the program's text size by using the ll command.

nstrpty = 60 may be fine if users do not login to the computer. There are 3 parameters that control the number of interactive sessions: npty, nstrpty and nstrtel. If the users will all connect to the Oracle database through special sockets, then 60 is probably fine. But if there are hundreds of users that will login to this specific machine every day, you'll need to bump all 3 to 500 or even 1000. Use SAM to make these changes because SAM will also take care of creating the required device files.

[Michael Ernstoff]

There are no users within Unix. This specific server is an Oracle Database server, and there are PC-based clients.

What is the likely impact of having maxdsiz_64 too low?

[Geoff Wild]

Here's mine:

RP7410, 11.11, 5CPU, 10GB:

Total VM : 10.8gb Sys Mem : 1.98gb User Mem: 6.91gb Phys Mem: 9.84gb
Active VM: 4.37gb Buf Cache: 806.4mb Free Mem: 171.7mb

N class, 11.0, 6 Cpu, 8GB:

Total VM : 255.5mb Sys Mem : 403.9mb User Mem: 2.03gb Phys Mem: 8.00gb
Active VM: 80.7mb Buf Cache: 819.2mb Free Mem: 4.77gb

Definately, drop your DBC_MAX_PCT if you are running Oracle. Oracle does it's own buffering.

My parms on 11.11 above:

dbc_max_pct 8
maxdsiz 0x40000000
maxssiz 0x800000
maxssiz_64bit 0x40000000
maxtsiz 0x4000000
nstrpty 60
semmni 1024
semmns 1024
shmmax 0x400000000
shmmni 256
shmseg 200


Rgds...Geoff