Re: UNICenter TNG Alert Oracle Database Server Memory hit 90%

Hi Timothy,

There are two "areas" of memory the Oracle uses.

The first area is the System Global Area (SGA) or the Shared Global Area, as this is a sharable area of memory that can be accessed by all connections to the database. This is made up of a whole bunch of components, the major ones being fully configurable via the database parameter file. Therefore the size of this is controlled by the DBA.

The second area(s) of memory are the Program Global Area (PGA) or Personal Global Area as this memory can only be accessed by each connection to the database. Each connection starts it's own server process which is assigned it's own PGA. The PGA is also made up of a bunch of components, some of which can also be controlled by parameters in the init.ora file. The point here though is that the more connections you have, the more PGA memory that is being consumed. If you have many connections, you can reduce the PGA memory consumption by instead configuring Multi-Threaded (or Shared) Servers which mean connections "share" a number of pre-allocated servers processes.

So the total memory used by Oracle is (effectively) the sum of the SGA and all the PGAs.

When you say that Oracle is using 80% of your memory and is that usual the answer is of course not. It depends on how much memory you have and how you have configured and sized the Oracle memory structures and how many connections you have (and whether or not you are using Shared servers).

If Oracle memory structures are paging this is going to really hurt performance.

My recommendation is to seriously look at tuning Oracle to ensure that memory is being allocated and used effectively and look at the number of connections you have to the database and consider moving to Shared Servers if appropriate.

The Performance Tuning manual might be worth a peep.

Cheers

Richard

"Timothy, Tung Mieng TAN" <tantm_at_novasprint.com> wrote in message news:3D912BBE.4010608_at_novasprint.com...
> Hi,
>
> I would like to know if anybody user any monitoring tools to monitor the
> Memory performance of Oracle Database Server?
>
> Currently my TNG server keep sending me alert message because my Oracle
> Database server memory has hit the threshold that I set. My threshold is
> set to 80%. And it seems like the memory is keep incresing so now I have
> to set the threshold to 90%.
>
> I would like to know if Oracle always use up all the available memory
> once it was started. Should I monitor the momory? Is 80% normal?
>
> regards,
> Timothy
>
Received on Wed Sep 25 2002 - 09:37:03 CDT