Obtaining Memory Sizing Advice for ASMM

The following steps describe how to obtain memory sizing advice when automatic shared memory management (ASMM) is enabled.

To obtain memory sizing advice for ASMM:

1. Go to the Database Home page.
   See "Accessing the Database Home Page".
   
2. At the bottom of the page, click Advisor Central.
   
3. On the Advisor Central page, click Memory Advisors.
   The Memory Advisors page appears.
   
4. On the SGA subpage, next to the Total SGA Size field, click Advice.
   
   The SGA Size Advice child page appears in a separate window.
   
   Description of the illustration sga-sizeadvice.gif
   
   Improvement in DB Time (%) is plotted against Total SGA size. A higher number for Improvement in DB Time is better for performance. In this sample figure, the graph indicates that increasing the SGA size greater than 450 MB results in no performance gain. Thus, 450 MB is the recommended optimal SGA size.
   Click OK to close the SGA Size Advice child page.
   
5. Near the top of the Memory Advisors page, click PGA to display the PGA subpage.
   
6. Next to Aggregate PGA Target, click Advice.
   The PGA Target Advice page appears, plotting cache hit percentage against PGA target size.
   The cache hit percentage is the percentage of read requests serviced by memory, as opposed to those requests serviced by reading from disk, which is slower. A higher hit percentage indicates better cache performance. The optimal zone for cache hit percentage is between 75 and 100 percent. However, it is not safe to conclude that your database is having performance problems simply because your cache hit percentage is not within the optimal zone. When the amount of currently available PGA memory is not adequate for optimal performance, ADDM automatically recommends adjusting this value in a performance finding.