November 22, 2006

SQL*Net more data from client

A while ago, OEM report some alert messages to us:

Wait class "Network" was consuming significant database time.  
Wait event "SQL*Net more data from client" in wait class "Network" 
     was consuming significant database time. 

We also see a 30ms slower to render our web pages.

According to Oracle doc,

SQL*Net more data from client
The server is performing another send to the client. The previous operation was also a send to the client.

It is not of much help.

The OEM gives a more clear indication:

Investigate the cause for high “SQL*Net more data from client” waits in Module “JDBC Thin Client”.

It is telling us that something is wrong with the JDBC drivers.

Chris May find a good article here

The cause of this event was a sequence of parse calls that passed excessively long SQL text strings through SQL*Net from the client to the server (instead of using stored procedure calls to accomplish the same thing). The long SQL text strings wouldn’t fit into a single SQL*Net packet, so the Oracle kernel spent a considerable amount of time awaiting second and subsequent SQL*Net packets during parse calls.

Hibernate, the ORM tools used by our application, generates long SQLs. Instead of select * from table, it use select col_1, col_2 from table.

After upgrading to latest JDBC driver, the problem fixed.

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