Thanks for your response.
Shortly after I posted my question, our customer decided to put the Linux port on hold, so we've moved all their transaction processors back to Windows 2000.
In the process, I was able to show that it was indeed the Microsoft SQL Server JDBC driver that was creating the scb_* files. It exhibited the same behavior on Windows 2000.
Hopefully in the not-too-distant future we'll be porting the transaction processors back to Linux. I think we'll try a different JDBC driver then.
Who know, by then the database servers might be Oracle on Linux...