VAST 4.5 - ODBC Calls Hang Using Abt Coroutine Calls 
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 VAST 4.5 - ODBC Calls Hang Using Abt Coroutine Calls

We have a server Smalltalk service running on NT Server 4.0 which uses
TOPLink 4.0 for VA.  Our service creates multiple database connections
to a Sybase 11 server.

Using standard ODBC API calls, the entire VM is blocked while waiting
for the results of the database call.  Instead of having a short lived
server request be penalized if a long lived request that is handled
first, we decided to make use of the CoRoutine calls provided by the
AbtDbm... applications.  TOPLink provides a database accessor
(TOPIBMODBCDatabaseAccessor) which makes use of these threaded calls.
As a result, if a database call is made by an SST dispatch worker, the
VM is not blocked and other SST dispatch workers can service other
requests while waiting for the result from the database.  This is
working fine, but when a number of user requests are being handled by
the smalltalk service (particularly those that involve begin/commit
transactions), we incurr a blocking situation in the database where one
connection is blocking other connections from completing their work.  It
is not apparent why the one connection (causing the blocks) is not
finishing its work and allowing the other connections to continue.
According to Sybase, the blocking connection is simply in a "Awaiting
Command" state.  No deadlock situations are appearing in Sybase.

As for server smalltalk, the service continues to accept new requests
and process them, but as soon as an SST dispatch worker tries to make a
database call, that SST dispatch worker is hung.  This happens for every
subsequent dispatch worker that tries to make a database call.  Things
don't get rolling again until we kill the connection from the Sybase
server end.

Has anyone seen this kind of behavior?  We've implemented a number of
low level logging messages in our image at the point where the ODBC API
calls are made and also display the return codes in an attempt to see if
Smalltalk is actually getting anything back from the ODBC layer.  We
will be testing this tomorrow.  In the meantime, I was wondering if
anyone had any tips regarding this.

Thanks in advance...Matt



Wed, 18 Jun 1902 08:00:00 GMT  
 
 [ 1 post ] 

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