Hello,
We are in process of migrating our servers to Windows 2008 OS and migrating
databases to SQL Server 2008, all from SQL 2000 ruing on Windows 2003.

When client application running on Windows 2003 server calls database
running on SQL Server 2008, all is great and response is fast.

However, when client is installed on Windows 2008, and tries to SQL Server
2000 database on another server, the response of query is noticeably slow.
Instead of taking say 0.5 seconds, same query against same database takes
several seconds, regardless of what query it is, which manifests itself in
significant drag on our web application. The query is simple select query.

Our application is a classic ASP web application. The ASP pages on web
server call DLLs on a dedicated application server via DCOM, which in turn
calls the database and returns results. We are using ADO 2.8 to connect to DB
to return simple recordset. The DLLs are written in VB6, and are registered
in COM+ application on the Application server, then exported and registered
on WEB server. Here is a typical connection string we use to call SQL Server
database (both 2000 and 2008) from the VB6 DLLs:
provider=SQLOLEDB;Server=SomeSqlServerName;Integra ted
Security=SSPI;database=SomeDB;

Identical problem occures with .NET DLLs wirtten in VB.NET using ADO.NET and
exposed via remoting. The .net DLLs are noticeably slower in extracting data
from SQL 2000 when the DLL is running on some server with Windows 2008; again
access if very FAST regardless of SQL server database version version when
identical DLL is installed on Windows 2003. The connection string we use for
our .NET DLLs is:
Server=SomeSqlServerName;Trusted_Connection=True;d atabase=SomeDB;

The slow response is present only when connection string is pointing at SQL
Server 2000 database, while DLL is running on top Windows 2008 OS. As soon as
you change the server name in the connection string to point the DLL at a SQL
Server 2008 machine, the speed returns to normal.

In other words the issue of performance is as follows:
Calling SQL Server 2008 from remote DLL on Windows 2003 => super fast
Calling SQL Server 2008 from remote DLL on Windows 2008 => super fast
Calling SQL Server 2000 from remote DLL on Windows 2003 => super fast
Calling SQL Server 2000 from remote DLL on Windows 2008 => extremely slow.

I can not find any way to remedy the problem.
I am thinking that there is some overhead created somewhere when Windows
2008 tries to call SQL Server 2000, perhaps client network libraries are not
talking to each other. I tried to install client connectivity tools/libraries
from SQL 2000 install CD on the Windows 2008 server where DLLs are running
(got compatibility warning) but it made no difference. We never actually had
to install any client libraries or tool on Windows 2003 to connect to any
version of SQL server. All that's needed (before this issue came up) was just
the registration of the DLL in COM+ server application, correct connection
string, and that's it.

Any help in how to remedy to speed degradation problem is appreciated.

Peter

"Erland Sommarskog" wrote:
Hello Erland,
Thank you for your reply and comments.

It appears the problem was due to Windows 2008 having trouble resolving
NetBIOS name of the remote SQL/Windows 2000 server.

This in turn caused delays in establishing connections to remote SQL 2000
server, putting drag on the entire application.

After putting the IP address of the remote SQL2000 server into HOSTS file on
the Windows 2008 server, the speed is back to normal.

So it appears that reason for latency was due Windows 2008 taking too long
to resolving NetBIOS names of remote SQL Server 2000 machine (running on top
of Windows 2000). This could have something to do with the fact that we are
not using any DNS or WINS on the segment. Or, maybe NetBIOS over TCP/IP
supported by Windows 2008 is not talking to that protocol on Windows 2000.

Regards
Peter

Peter_April1 (PeterApril1 (AT) discussions (DOT) microsoft.com) writes:
Whatever, that sounds like a topic for a Windows newsgroup. In other words,
it goes waaaay over my head.


--
Erland Sommarskog, SQL Server MVP, esquel (AT) sommarskog (DOT) se

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