This is just a short blog post about a simple DTrace script (dtrace_kghal_pga_code), that i recently wrote and published due to a PGA memory leak troubleshooting assignment. A client of mine noticed a major PGA memory increase after upgrading to Oracle 12c. The PL/SQL code did not change - just the database release. He already troubleshooted the issue with help of Tanel Poder's blog post "Oracle Memory Troubleshooting, Part 4: Drilling down into PGA memory usage with V$PROCESS_MEMORY_DETAIL" and identified the corresponding heap and allocation reason.
Last week the DOAG 2014 conference took place in Nuremberg and it was a blast with a lot of useful presentations and especially great conversations and meet ups with Oracle friends. I had a nice talk about the Oracle latch implementation with a participant, who told me that his instance crashes every time, if he (manually) sets a shared latch in exclusive mode and tries to release it afterwards. It sounded really interesting as i have done this so many times without ever noticing such an issue. He also told me that this issue is reproducible at least on Oracle 11g R2 and 12c R1. I had no immediate answer or clue about the described issue and needed to research it furthermore.
A long time has gone since my last blog post on SCN in March 2014, but i was quite busy with Oracle RAC implementations and troubleshooting performance issues in the last month. It was a quite interesting time for me and i have learned a lot of new stuff about Oracle 12c and so in consequence this is just a tiny blog post about a new diagnostic event called "wait_event", which was introduced with Oracle 12c R1 (126.96.36.199). Oracle has re-engineered its kernel diagnostics & tracing infrastructure with Oracle 11g, which allows you to be much more detailed and extensive by tracing and dumping diagnostic / low level (internals) information. Please check the reference section for more detailed information about that "new" kernel diagnostics & tracing infrastructure, if you have never heard of it until yet.