During the install of a Package, a temporary file _UPGRADE.LCK is created in the root directory of the application being processed.
This file prevents different installations of the Application from running the upgrade simultaneously on the same PC. The file is removed when the upgrade is completed.
If a lock is found during the upgrade, the application upgrade's behavior will be governed by the settings for the Connection failure action (UPCF=) parameter.
Refer to the Connection failure action (UPCF=) in Just in Time Options for details of this parameter.