- Emergency monitoring is meant for extreme circumstances where it’s impossible for you to connect to the database because the database is hung.
- Emergency monitoring allows you to connect to the database in diagnostic mode and run a lightweight analysis to see what’s happening.
- You can access real-time performance data from ASH and access the hang analysis data.
- Unlike in 11g, you don’t have to explicitly activate the memory access mode, emergency monitoring connects directly to the SGA to retrieve the necessary data.
- Real-Time ADDM unlike Emergency Monitoring is used to analyze the root cause of the hung.
- Real-Time ADDM works like the normal ADDM but access only the last 10 minutes of ASH data to provide recommendations.
- Because Real-Time ADDM only uses data from memory you can still access it when the database is hung.
- You can use Real-Time ADDM triggers to proactively monitor the performance of an instance.
- High load
- I/O bound
- CPU bound
- Over-allocated memory
- Interconnect bound
- Session limit
- Process limit
- Hung session
- Deadlock detected
- Reports can be viewed in DBA_HIST_REPORTS and DBA_HIST_REPORTS_DETAILS.
- To manually generate a report you can use the following procedure
SQL> select dbms_addm.real_time_addm_report() from dual;
- You can also generate an ADDM report using the EM Database Express by going to the performance hub et click on “Current ADDM findings“.