When you use the WCF-OracleDB adapter in BizTalk Server, and many sessions are running, the Oracle server experiences a heavy load.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This problem is fixed in the following cumulative update for BizTalk Server:
For information about the service packs and cumulative update list for BizTalk Server, see the following article in the Microsoft Knowledge Base:
2555976 Service pack and cumulative update list for BizTalk Server
For more information about BizTalk Server hotfixes, see the following article in the Microsoft Knowledge Base:
2003907 Information about BizTalk hotfixes and Cumulative Update support