Use of Memory

[Gamaliel]

Hi,

I have this situation:

2 HP UX servers 11.11
4 GB Physical Memory
Sybase ASE running

Whe I start SYBASE ASE on one of them, I configured to use 1.5 GB of Memory and start 2 processes, and so it works, each process uses 750 MB

On server 2 I configured SYBASE ASE to start 4 processes and to use 3 GB of Memory, but even it starts the 4 processes, each process only uses 175 MB when it must be 750 MB/Process

Any ideas?

[V. Nyga]

Hi,

check kernel settings.

You can do a 'kmtune > test.txt' at both servers and compare it with 'diff'.
Check the differences.

Volkmar

[Gamaliel]

Hi,

The different parameters are:
dbc_max_pct
max_thread_proc
max_swapchunks
semmnu

Two more things:
-) The "m" option of glance reports an increment use of memory on Sys Mem and Buf Cache, is that normal? How can I see the detail of how that memory is being used?
-) The "M" option for the sybase process displays the memory asigned to the DB Server.

[TwoProc]

My bet is on dbc_max_pct.

Set the both the same, or set them both at something like 5.

[V. Nyga]

Hi,

you can align the parameters with SAM.
As root: 'sam' - 'Kernel Configuration' - 'Configurable Parameters'

The system will reboot after this!

V.

[Gamaliel]

Hi everyone,

I already change dbc_max_pct from 20 to 10 %, dbc_min_pct was at 5 % so i don't make a change. The server that was working well had dbc_max_pct at 50 %a, although it doesn't have problems. After change i saw the disk resource at 100% several times in the morning, of course after a full day the average is about 60%

More sugestions?

[Michael Steele_2]

Send your 'swapinfo -tam' information and verify that swap is identical on both machines. Check for pageouts and memory allocated to other processes, vmstat. For example, if another process is consuming memory before SYBASE starts.

Consider rebooting the culprit machine to clear swap.

Consider increasing db_cache_size and shared_pool_size when lowering dbc_max_pct.

lower dbc_max_pct to 10
increase db_cache_size
increase shared_pool_size

[A. Clay Stephenson]

THe most likely explanation is simply that the application (Sybase) is configured differently on the two boxes; that's the first thing that I would check.

You should note that from a process perspective it doesn't matter how much physical memory is in a box (although that will make a huge performance difference) but rather the total amount of virtual address space configured.

It would be good to know if this is a 32-bit or a 64-bit application and whether you are measuring data size or shared memory for these processes. I assume this is a 32-bit process. A very important tunable to check is maxssiz because both data and stack are allocated from the same 1GB quadrant. For example, if maxssiz were set to 600MB and maxdsiz were set to 1000MB, the maximum possible amount of dynamic memory allocation would be 400MB whether or not the actual stack ever approached 600MB. You should set maxssiz to no more that 64MB (and that is very generous).

[Gamaliel]

None