Starting from 6.0, the jobname.lock lock file is generated to prevent multiple runs with the same jobname from being executed from the same working directory.
To disable this feature, set the environment variable "ANSYS_LOCK" to "OFF".
For details, please refer to the documentation, either: "Installation and Configuration Guide for UNIX", Ch. 4.2.7 Setting Other Environment Variables, or "Installation and Configuration Guide for Windows", Ch. 4.1.5 Setting Other Environment Variables.