A client regularly uploads an Access database (I know, I know, not the best one for the job.. but the point is another blog/argument) which is then a CFMX7 datasource.
Occasionally and intermittently over the last few years, the .mdb file would be locked, showing the corresponding .ldb file and the uploads would fail. But these files weren't just locked. They were so tightly bound, that FTP deletes would not delete. Even the hosting support personnel could not delete. They had to shut down the CF server, and IIS to delete the files and then restart. Not good news for other accounts the shared hosting server.
Even more interesting is that all of a sudden, the problem became more frequent (locking 6 times yesterday, and 5 more today)... and thus, replicable. It appears as if CF Access datasource connection creates the lock (appropriately) when a query of any sort is performed, even SELECT statements. Attempting an upload while the file is "locked" however doesn't just reject the upload, it corrupts the files and the service.
We don't know what changed, but every single upload now locks. and I suspect the java method that creates the datasource link may lock the database at the application.cfc level. (Any CF/JAVA wizards, please feel free to chime in on this suspician if you know one way or the other). IIS is v6.
To correct this, have the CF Administrator UNcheck that the "maintain database connections" . Creating a "dummy" query is only for pre CF6.