- our EPR system uses Progress database (blackbox for me, don't even know where it is installed)
- on a Windows Server 2003 instance we have a ODBC datasource (System DSN), which uses OpenEdge 10.1C driver and is connected to the Progress database. The driver's isolation level is 'read uncommitted'
- on the same Windows system there is a SQL server 2005 installed and if I run 'dbcc useroptions' in one of the database, the isolation level is set to 'read committed' (althoug I doubt that this has any relevance in my example)
- on the SQL Server 2005 we have a linked server to the Progress database, which uses the ODBC data source
- we query Progress database via the openquery command, simplified:
from openquery(LINKED_SERVER_NAME, '
select distinct Country
where Id = 10
The problem is, that sometimes the query throws
Cannot fetch a row from OLE DB provider "MSDASQL" for linked server "LINKED_SERVER_NAME"
exception. As I profiled the execution of the query, I saw that the exception is thrown by the OpenEdge driver:
OLE DB provider "MSDASQL" for linked server "LINKED_SERVER_NAME" returned message "[DataDirect][ODBC Progress OpenEdge Wire Protocol driver][OPENEDGE]Failure getting table lock on table XXX.Countries"
So it seems, that the query tries to lock the XXX.Countries, although the OpenEdge driver is set to 'read uncommitted'. Why is this happening?
I will try to play with various settings (isolation level on database level, set transaction isolation level in each transaction, ...) and do a thorough profile for each query, but this will be time consuming and also - the exceptions is thrown randomly so it is hard to profile. Any additional informations about this topic would be much appreciated.