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Communication link failure

My application (a commercial application written in Powerbuilder) is frequently crashing and the following error message is recorded in the application's log:

SQL Error Text:  Select error: SQLSTATE = 08S01
[Microsoft][ODBC SQL Server Driver]Communication link failure

Based on Google searches this indicates the LAN connection was dropped.

The database is MS SQL Server 2000.  The server is an HP Proliant ML370.  The switch is an HP Procurve 2650.  The workstations are P4, WinXP, 512MB RAM, NeXtreme Gigabit Ethernet.  The cabling is CAT5E.

The Procurve switch sofware indicates zero network errors.

Set the server and workstation NIC speeds to 100HDx.  (No improvement).
Checked the physical connections which appear to be okay.
Ran diagnostics on the NIC cards.  No problems were reported.

What else should I be checking?  

Thank you.

Brian



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bmcasey
Asked:
bmcasey
1 Solution
 
SweatCoderCommented:
We have had this same exact problem at my company. Our sysadmin SWEARS there's nothing wrong with the network or the hardware/connections. It seems like we switched the DB from one server to another and that fixed it.

If you could put your sqlserver on the same machine as the app, the problem would go away, but I don't know if that's feasible for you.

It seems to me that sqlsvr is not very robust in this scenario. If the connection is unavailable for a millisecond it just gives up instead of keep trying.

As another alternative, I wonder if in your powerbuilder code you could *catch* the db connection error and keep trying x number of tries, and maybe that would solve it.
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bmcaseyAuthor Commented:
It wouldn't be feasible to put sqlserver on the same machine as the app.  There are several users sharing the database.

One of the Google results suggested coding the application to either test for a connection and then connect if the connection didn't exist or, as you suggested, try x times to connect.  This is a commercial app so I'd need to convince the vendor to make these changes.  The vendor thinks its a network problem (and it may be) but, most of the network is brand new - cabling, server, workstations and switch.  The diagnostics so far haven't produced any errors.  The vendor suggested "dumbing down" the NICs to 100HDx.

Thanks.
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arbertCommented:
"Our sysadmin SWEARS there's nothing wrong with the network or the hardware/connections."


You have to remember, the communication link failure error isn't always network related.  Sometimes a server can get busy and will simply not answer the request--it yields a communication failure, even though it wasn't a network problem.

Personally, to eliminate possibilities, I would fire up SQL Profiler and take a look at the activity hitting the server.  Also, look at windows perfmon and see what the IO and memory usage looks like (an IO bound server will also cause connections to get "communicaiont link failure" errors).
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bmcaseyAuthor Commented:
Sorry.  I didn't mean to abandon the question.  While neither specifically answered the question, I appreciate Sweatcoder's and arbert's replies.  Arbert's recommendation to use SQL profiler and Windows perfmon were good ones.  If I were more familiar with these tools they problably would have been more helpful.

As it turned out our vendor discovered a coding defect which hung the workstation, the user would recycle Windows to recover from the hang.  This would cause records to be locked which would in turn cause the application hangs downstream when other users tried to access/update those same records.

This is the first question I have asked and also the first one I'm closing.  I read the link you provided above but, it is not clear to me how to close this question fairly.  I'd appreciate your suggestions.  Thank you.

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arbertCommented:
"Arbert's recommendation to use SQL profiler and Windows perfmon were good ones.  If I were more familiar with these tools they problably would have been more helpful.

As it turned out our vendor discovered a coding defect which hung the workstation, the user would recycle Windows to recover from the hang.  This would cause records to be locked which would in turn cause the application hangs downstream when other users tried to access/update those same records"


Profiler would have caught this.   You really should have responded and said you didn't know how to use the tools or needed more information--we can't read minds.  I think my answer was pretty on target, but what ever....
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moduloCommented:
PAQed with points refunded (250)

modulo
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