db2 problem increasing buffer pools after RAM upgrade

[m***@yahoo.it]

I have db2 8.2 installed on LPARs with RHEL 4.3 on a IBM pSeries p570.
I upgraded a LPAR from about 7,5GB to about 10,5GB.
Before upgrade I had a bufferpool of about 5GB. After the upgrade I tried to recreate the bufferpool larger but connecting to the database it return the error regarding insufficient memory. i.e. I tried to create a bufferpool of about 9GB and it failed. Trying about 7GB is ok. Trying a little bit more fail again. I tried on another LPAR upgraded from 1GB to 3GB and this appen: I am able to create a bufferpool until 7GB (notice the phisical RAM is 3GB) with connection to the db resulting in a success. After 7GB it fails again stating insufficient memory. I'm quite confused. I don't understand if the problem is related to the absolute value of 7GB, to the act of upgrading the RAM or wath else. Anyone faced a similar behaviour?

[l***@ca.ibm.com]

Hello,

Please take a look at your shmall kernel setting - that limits the total amount of shared memory that can be allocated on the entire LPAR (DB2 buffer pools are allocated using shared memory). The default is 8GB - I'd suggest increasing your shmall setting to be about the same as the RAM you have configured on your machine.

Cheers,
Liam.

[m***@yahoo.it]

Great!!!
It solved my problem!
Exatly this parameter is expressed in number of pages of 4KB. So it has to be set at the value of ram divided by 4KB.

Thank yuo very much!