share my expierience

Every database upgrade is a challenge for DBA to make it smoothly and without pain. Recently I did one, upgraded RAC database to 11.2.0.2 + PSU5. After major post upgrade problems were fight I started to check performance, overall feeling was well but of course there were some bad SQL to be tuned and I noticed event I didn’t know yet and that was bothering me. This is how stats pack report look like:

Top 5 Timed Events                                            Avg %Total
~~~~~~~~~~~~~~~~~~                                           wait   Call
Event                                    Waits    Time (s)   (ms)   Time
--------------------------------- ------------- ----------- ------ ------
CPU time                                            21,587          44.9
db file sequential read              2,272,181       8,247      4   17.1
GCR sleep                                1,434       7,185   5010   14.9
db file scattered read                 629,679       2,865      5    6.0
enq: TX - row lock contention            3,291       1,786    543    3.7

And I couldn’t understand what is this sleep/wait event that occupies 15% of system resources and how I cannot see it from application performance or concurrent processing point of view . As neither MoS or google could help me SR was raised and this is what we get:

The GCR sleep event is an Idle Wait Event. This event should not be included by statspack when reporting on the Top Timed Events.
The following internal bug covers this issue:Bug 9695145 STATSPACK STANDBY: UPGRADE SCRIPT MISSING NEW IDLE EVENTS
This bug will be fixed in the next patchset release (11.2.0.4) Please ignore the GCR sleep Event as it does not represent a performance issue.

So no worries, this is just a representative bug into Oracle Statspack.
How can I trust Statstpack now? :)