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RAC Failover : Missing Sessions Reconnected with TAF [message #398784] Fri, 17 April 2009 09:25
TomG
Messages: 11
Registered: December 2008
Junior Member
Hi,

I'm testing Oracle RAC (10.2.0.4 64bit on 2 nodes Linux RHEL5 x86-64) with some failure scenarios.
I stress the database with :
- 100 users connections on a service.
- For all TAF is enabled with at SESSION level with BASIC method
- Connetions are Load balanced across 2 instances :

select inst_id, count(username) from gv$session where username not in ('SYS', 'SYSTEM') and username is not null group by inst_id;

   INST_ID COUNT(USERNAME)
---------- ---------------
         1              51
         2              49


When I shutdown a node I can (sometimes) see that some sessions are not reconnected on surviving instance :

   INST_ID COUNT(USERNAME)
---------- ---------------
         2              76    <--<< 24 sessions are missing !


When I checking surviving instance alert.log I can see that same number of "GCS Shadows" are closed :

 ...
 * dead instance detected - domain 0 invalid = TRUE
 Communication channels reestablished
 Master broadcasted resource hash value bitmaps
 Non-local Process blocks cleaned out
Fri Apr 17 16:00:11 2009
 LMS 0: 14 GCS shadows cancelled, 11 closed  <--<< 
Fri Apr 17 16:00:11 2009
 LMS 1: 13 GCS shadows cancelled, 13 closed  <--<< 
 Set master node info
 ...

1. The "GCS shadows cancelled, XX closed" alert.log entries seem match my missing number of sessions. Is that true ?
2. I know what GCS is but but I don't understand why it occurs. Any clue ?

Thanks for help
Tom

[Updated on: Fri, 17 April 2009 09:29]

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