Here is a quote from the manuals.  I guess it depends on whether you are 
using DB links, which we are...

General XA Issues and Restrictions
Database Links
Oracle XA applications can access other Oracle Server databases through 
database links, with the following restrictions:

Use the Multi-Threaded Server configuration.

This means that the transaction processing monitors (TPMs) use shared 
servers to open the connection to Oracle. The O/S network connection 
required for the database link is opened by the dispatcher, instead of the 
Oracle server process. Thus, when a particular service or RPC completes, the 
transaction can be detached from the server so that it can be used by other 
services or RPCs.

Access to the other database must use SQL*Net Version 2 or Net8.

The other database being accessed should be another Oracle Server database.

Assuming that these restrictions are satisfied, Oracle Server allows such 
links and propagates the transaction protocol (prepare, rollback, and 
commit) to the other Oracle Server databases.


--------------------------------------------------------------------------------
Caution:
If these restrictions are not satisfied, then when you use database links 
within an XA transaction, it creates an O/S network connection in the Oracle 
Server that is connected to the TPM server process. Because this O/S network 
connection cannot be moved from one process to another, you cannot detach 
from this server. When you access a database through a database link, you 
receive an ORA#24777 error.

--------------------------------------------------------------------------------




If using the Multi-Threaded Server configuration is not possible, then 
access the remote database through the Pro*C/C++ application using EXEC SQL 
AT syntax.

The parameter open_links_per_instance specifies the number of migratable 
open database link connections. These dblink connections are used by XA 
transactions so that the connections are cached after a transaction is 
committed. Another transaction is free to use the dblink connection provided 
the user that created the connection is the same as the user who created the 
transaction. This parameter is different from the open_links parameter, 
which is the number of dblink connections from a session. The open_links 
parameter is not applicable to XA applications.








----Original Message Follows----
From: "zhu" <chao_ping@v...>
Reply-To: "Oracle" <expert_oracle_performance@p...>
To: "Oracle" <expert_oracle_performance@p...>
Subject: [expert_oracle_performance] Re: Shared Server requirement for XA 
applications
Date: Tue, 4 Mar 2003 06:40:15

Is it really necessary?
We are using XA and Oracle 817/920, without shared server.

zhu chao.

 > Hi Tom.

 > Just thought you might want to mention that Shared Server is a
requirement
f> or XA based applications.  So, if you use XA, you must use shared
s> erver.  Might be worth considering adding to the chapter.

 > Brad


_________________________________________________________________
Protect your PC - get McAfee.com VirusScan Online  
http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963