You can click the Monitor In Memory Access Mode link in the Related Links section to enable Memory Access Mode. The Database Performance page reappears with a Disable Memory Access Mode button and a Switch to SQL Access Mode button in the upper right corner.
You can temporarily disable Memory Access Mode by clicking this button, upon which the Database Performance page reappears in SQL Access Mode. To reactivate Memory Access Mode, click the Monitor In Memory Access Mode link again, then click Enable Memory Access Mode when the Database Performance page reappears.
In Memory Access Mode, performance statistics are retrieved directly from the Shared Global Area (SGA) using optimized/lightweight system-level calls as an alternative to SQL. Memory Access mode avoids the computation associated with parsing and executing SQL statements, thereby making it ideal for severe cases of library cache contention that can prevent the instance from being monitored in SQL Mode. You should switch to Memory Access Mode for slow or hung systems.
Pages in Memory Access Mode contain data sampled at a higher frequency than pages in SQL Mode. (Charts may appear to be slightly different from SQL mode for this reason.) Consequently, Enterprise Manager provides better information about where events begin and end, and can also handle short-duration events that might otherwise be missed.
Using Advisors to Optimize Database Performance
Using the Advisors to Verify SQL Performance
Enterprise Manager Information Roadmap
Copyright © 1996, 2010, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.