The dlm document describes a return status of EDEADLOCK and this is referenced in ast.c and a couple of the tests. Using the latest version of CVS (I'm pretty sure) I can't find the definition for EDEADLOCK in a header file. The only definition is in one of the tests (which doesn't build) and it defines it as SS$_DEADLOCK :-) [Neither of the tests in the dlm\tests\locktest directory compile cleanly] I assume I'm missing something but I'm not sure what it is.