Here is the followup to my previous blog post Getting Latch holder info out of the state objects in SGA memory where i described how we can extract latch state objects directly from the SGA memory. So let’s begin !
It will be great to have a tool that will extract latch holder information directly from state objects stored inside the SGA. This way we will reduce the overhead when troubleshooting latch contention an beside that it’s also cool !!
This may sound difficult ! How to proceed ? and the answer is …. Memory reference tracing !
Since oracle 22.214.171.124 Adaptive Dynamic Sampling result are stored inside SPD as a special directive type “DYNAMIC_SAMPLING_RESULT”. This will allow the result of ADS to be persisted on disk,thus it will survive memory flush and database restart.For more detailed info please check Mauro Pagano blog Post Something new about SQL Plan Directives and 12.2
We may ask at this moment is there some sanity check that will trigger the refresh of this ADS result stored as sql plan directive when the table data is marked stale (STALE_PERCENT) ?
“Improving the PL/SQL Debugger:
In prior releases, it was necessary to change the application to include calls to start and stop debugging. With this improvement, one database session can start debugging, and stop debugging a different session.”
“With these improvements, if a problem occurs in a long running test or in a production environment, it is possible to investigate the problem from another session.” Oracle Database 12c Release 2 (12.2) New Features
Let’s take a closer look :
In one of my previous blog post i demonstrated that the amount of work needed for IN-MEMORY population/[trickle] re-population in oracle 126.96.36.199.6 is more than we may expect : IN-MEMORY population/[trickle] re-population : How much work ? You may be surprised !
Let’s do a very quick check on how this is now handled in oracle 188.8.131.52/OEL 6/UEK4
This is my third blog post about an issue that we may encounter with uprobes and the recent kernel/oracle version.
- Part 1 :uprobes issue with oracle 12c
- Part 2 :Workaround for Linux Perf Probes issue for Oracle Tracing
As the name of this article suggest i will show here how we can put a probe point on oracle functions using systemtap based on the workaround that i described previously.