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Kernel parameters and SGA size

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Alexander Ivukov
Occasional Visitor

Kernel parameters and SGA size

I have L2000 1 Gb RAM, 2 Gb swap, HP-UX 11.0 and Ora 8.1.7 64 bit. After i add memory up to 6 Gb, i want increase SGA size. What kernel parameters i must change? Current parameters (for 1 Gb RAM) is set recommended by Oracle.
11 REPLIES
Praveen Bezawada
Respected Contributor

Re: Kernel parameters and SGA size

Hi Alexander
You have to increase the SHMMAX, this is the maximum size of a single shared memory segment and directly converts to the Shared memory that Oracle can use.
If you also want to increase the total number of shared memory segments, increase SHMMNI, this is number of shared memory indentifiers on the system.

Hope this helps.

...BPK...
Alexander Ivukov
Occasional Visitor

Re: Kernel parameters and SGA size

Hi Praveen!
What your say about maxdsiz_64bit?
Praveen Bezawada
Respected Contributor
Solution

Re: Kernel parameters and SGA size

Hi Alexander
On a 4GB L2000 running Oracle( 32 bit) and Java application we use maxdsiz of 1GB. But this value was decided after tuning the Java application.
I am not so sure if tuning of maxdsiz is required for Oracle. I suggest you try running it with 1 GB and see.

...BPK...
Jean-Luc Oudart
Honored Contributor

Re: Kernel parameters and SGA size

Hi Alexander,

you may check the following document on the Oracle Metalink Web site :
doc id 68105.1

JL
fiat lux
CHRIS ANORUO
Honored Contributor

Re: Kernel parameters and SGA size

Jean-Luc Oudart, you need to be registered before you access the metalink resources.
SHMAX of 1gb is ok. Search for my kernel configuration and use the parameters. Remember your swap space has to be increased.
When We Seek To Discover The Best In Others, We Somehow Bring Out The Best In Ourselves.
Alexander Ivukov
Occasional Visitor

Re: Kernel parameters and SGA size

Chris!
Oracle is not started if increase SGA parameters (for instance - pool size) - not enough memory. shmmax is set 1 Gb.
Andreas D. Skjervold
Honored Contributor

Re: Kernel parameters and SGA size

Hi

As long as the use of the database don't change (number of users) and all you want to do is enlarge the SGA (preferably the db_block_buffers) into the new 6GB of RAM, increase the SHMMAX kernel parameter to 6GB or at least the value you plan have for your new SGA.

Thus getting the SGA into a single shared memory segment.

The SHMMNI should be left unchanged as the number of shared memory segments don't change (unless you add another database)

To avoid having to add lots of swap space to accomodate the processes be sure to set swapmem_on = 1 in your kernel. This turns on psuedo swap and allows for more processes to be started than there is infact swapspace available for. You don't want your SGA to swap anyway so why set aside swapspace for it!


Andreas
Only by ignoring what everyone think is important, can you be aware of what everyone ignores!
Jean-Luc Oudart
Honored Contributor

Re: Kernel parameters and SGA size

Chris,

I assume that if you're using Oracle you're an Oracle customer (with support) abnd therefore you can register to Metalink !

Lots of stuff if you are an Oracle DBA !

JL
fiat lux
Praveen Bezawada
Respected Contributor

Re: Kernel parameters and SGA size

Hi Alexander
What are the changes that you have done before restarting the database ?
What is the error message that is being displayed ?

...BPK...
Alexander Ivukov
Occasional Visitor

Re: Kernel parameters and SGA size

Praveen,
my changes init.ora:
# Begin For 1Gb RAM
db_block_size = 8192
db_block_buffers = 18750
shared_pool_size = 300000000
log_buffer = 1048576
large_pool_size = 67108864
java_pool_size = 30000000
sort_area_size = 1048576
sort_area_retained_size = 262144
# End For 1Gb RAM
# -----------------
# -----------------
# Begin For 6Gb RAM
#db_block_size = 8192
#db_block_buffers = 393216
#shared_pool_size = 524288000
#log_buffer = 5242880
#large_pool_size = 104857600
#java_pool_size = 104857600
#sort_area_size = 10485760
#sort_area_retained_size = 1048576
# End For 6Gb RAM

You right - SHMMAX
Aashish Raj
Valued Contributor

Re: Kernel parameters and SGA size

I assume you are on 32 bit hp-ux , you can not increase the SGA beyong 1.75 GB even though you have 6 GB of memory.To take advantage of 6 GB memory, intall 64 bit hp-ux and 64 bit oracle.

thanks
AR