Last updated on AUGUST 26, 2007
Applies to:Oracle Net Services - Version: 188.8.131.52 to 10.2.0.3
Oracle Application Object Library - Version: 11.5.10 to 11.5.10
This problem can occur on any platform.
This Note is applicable for the topology and circumstances that are given below
* Application server concurrent managers environment, setup for PCP fail-over.
* Fail over is triggered when node running the ICM goes down
* This ICM going down would lead to connected database server process
clearing its resources (including named PL/SQL lock)
* In turn, the database server process cleanup is dependent
on DCD mechanism of network (sql*net)
* That is, sqlnet determines that connected client has closed down
through DCD mechanism and triggers database server process cleanup
The abbreviations in the document are
DCD => Dead Connection Detection
ICM => Internal Concurrent Manager
IM => Internal Monitor
DB => Database
PCP => Parallel Concurrent Processing
CP => Concurrent Processing
Here is the dependency on ICM and IM on the DCD functionality of the Network(sqlnet).
ICM which is a client process connected to DCD enabled DB dedicated server process.
ICM holds the named PL/SQL Lock.
IM is continuously trying to check whether it can get the same named PL/SQL Lock.
As soon as this lock is released by DB upon the ICM crashing,
IMON and thus, CP detects that ICM had died or crashed.
The DCD comes into picture here after ICM has crashed and DB need to
identify that ICM has gone.
After that DB need to clean up the dedicated server process resource
corresponding to the ICM client process.
Our focus from network perspective is only on the point (B) and
neither on the design model/ logic/functionality (A) nor on (C),
the resource clean up corresponding to dedicated server process after
detecting that ICM client has gone.
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