The simplest, and most compatible method, is to use a separate table with one row in it as the lock, simply update that row as the first operation in your transaction and all other accesses will serialize behind it. Or you could just ‘lock table blah in exclusive mode’ dunno whether that’s supported in all DB servers though. You can get smarter too, but it’s only worth it if you were going to do a lot more work in the txn and wanted to maintain parallelism.

All instances of my cgi script perform a read operation followed by a delete operation. Essentially, my script reads the top row from the database. Right after the information is retrieved that particular row is deleted. In other words, I am using my database as a FIFO buffer. Now if several instances of my scripts are running, more than one of them could access the first row (read it), thereby letting two different processes fetch the same element from a FIFO. One of them then fails with the deletion operation. The whole idea behind this locking mechanism was to avoid this. All instances of my script should always fetch a different item.

I will explore these techniques further to see if they could help me better solve my problem.