RE: System Wait Event Type

From: Yuval Arnon <Yuval.Arnon_at_wwfent.com>
Date: Tue, 07 May 2002 13:05:19 -0800
Message-ID: <F001.0045A82D.20020507130519@fatcity.com>

Tom,

Description:

This latch protects the pool of virtual circuit state objects. Virtual Circuits latch is acquired when a virtual circuit is allocated by a dispatcher, moved between the dispatcher and a shared server or when it is terminated. Moving a virtual circuit means that the ownership of the virtual circuit state object gets moved from the dispatcher to a shared server and vice-versa.

Functionality:

A dispatcher acquires the Virtual Circuits Latch to create a virtual circuit for every client connected to it. The virtual circuit created is used to send client requets to servers and receive responses from them.The request queue is picked by any shared server but the servers response queue is picked by the same dispatcher that created the virtual circuit in the first place.

Latch Contention:

               Very rare but it is possible when numerous connections are lost

               and being re-established within a small window of time, in this

               case one should find out the reason why dispatchers lost connections.

               Contention can also be caused by a blocked listener, a number of

               sessions then appear to abort or timeout. Restarting the listener

               clears the problem in most of the cases.   

               It is easy to detect Virtual Circuit Latch contention, it appears

               as "virtual circuits " wait event in both system state dumps and

               v$session_wait.

-----Original Message-----
Sent: Tuesday, May 07, 2002 4:44 PM
To: Multiple recipients of list ORACLE-L

All,  

I am running a long-running PL/SQL procedure (loading data). The procedure is getting all of the data from another database via a db link. There is one large driving cursor, with many sub-selects taking place to construct the records tobe inserted.  

I was monitoring the run, and noticed from the v$system_event table that the largest wait event in "virtual circuit status" followed by "db file sequential read"  

Anybody know what "virtual circuit status" is? My guess is it's from the database link.  

Any help would be appreciated.  

thanks  

Tom Mercadante
Oracle Certified Professional  

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Author: Yuval Arnon
  INET: Yuval.Arnon_at_wwfent.com

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