Change PGA for session?

Question

Hi there,
we are developing an OLTP application on 11gR2. As a consequence of having a lot of small transactions, we have configured a relatively small PGA and a lot of SGA memory and have configured the optimizer relevant parameters for choosing b-tree index paths.
Still we are going to have some batch Jobs, running during the non-office hours. Now my problem is, how to change the DB configuration session-wise, to be more DWH-like. While I can change the optimizer settings session wise, I have problems changing the PGA for a session.
How would you solve the problem? One solution could be to change from automatic PGA memory management to manual, that is to setting the %_AREA_SIZE parameters. These parameters can be changed session wise. But this would very much affect the behaviour of the overall system.
Any idea? What is the standard solution for such issues?
Many thanks in advance.

Answer 1

Centinul wrote:
user8768362 wrote:
Thanks but I mentioned this before in my own posting. I would somehow want to keep the automatic worksize area management.You can use manual PGA management at the SESSION level as Dom said, by changing the WORKAREA_SIZE_POLICY parameters, and subsequently setting the AREASIZE parameters.
user8768362 wrote:
and have configured the optimizer relevant parameters for choosing b-tree index paths.Would you be able to elaborate more on this? This sounds like a questionable change to me.
>
>Thanks but I mentioned this before in my own posting. I would somehow want to keep the automatic worksize area management.
You can use manual PGA management at the SESSION level as Dom said, by changing the WORKAREA_SIZE_POLICY parameters, and subsequently setting the AREASIZE parameters.
user8768362 wrote:
and have configured the optimizer relevant parameters for choosing b-tree index paths.Would you be able to elaborate more on this? This sounds like a questionable change to me.
>
>
Thanks but I mentioned this before in my own posting. I would somehow want to keep the automatic worksize area management.
You can use manual PGA management at the SESSION level as Dom said, by changing the WORKAREA_SIZE_POLICY parameters, and subsequently setting the AREASIZE parameters.
Thank you, that's it I think. My misunderstanding was that I had only looked at the PGA_AGGREGATE_TARGET parameter. Setting this parameter to 0, automatically sets the workarea_size to manual. Only difference is: pga_aggregate_target can only be changed on the system and not on the session level. So my solution is to change the workarea_size parameter to manual in the session and to set the xxx_area_size parameters as necessary. Thanks for the help. Sometimes the solution is there, but you just don't see it. :-)
>
user8768362 wrote:
and have configured the optimizer relevant parameters for choosing b-tree index paths.Would you be able to elaborate more on this? This sounds like a questionable change to me.Don't worry about that. I have made very good experience with these settings. I actually got the idea some years back from the book of Tom Kyte "Effective Oracle by Design". The default values
optimizer_index_caching              integer     0
optimizer_index_cost_adj             integer     100are good for DWH environments. For OLTP apps the following setting can be better:
optimizer_index_caching              integer     90
optimizer_index_cost_adj             integer     25As you know the cost estimations of the optimizer are relative. So these parameters influence the decisions of the optimizer to rather choose index-paths or rather full table scans. The OLTP settings have been proved in my projects as recommendable.
Thanks.