A Deadlock error is the system indicating that two or more processes on the server have collided. When you encounter a deadlock, it means that one process needed to be cancelled by the system. This can be due to resource shortages, or due to duplicate processes running simultaneously and trying to use the same tables at the same time.
You can usually resolve a Deadlock error simply by waiting a couple minutes and trying your action again.
If you get repeated Deadlock errors on the same action then you will need to terminate the excess process, up to and including restarting the server. If a server restart is required check to ensure no aberrant data conditions arose due to the deadlock.
