The following command is run to gain details on deadlocks.

 DBCC TRACEON (1222,-1)

However, once the SQL instance is restarted this flag is set back to disabled.

To enable it on the instance upon startup:

1. Open SQL Configuration Manager
2. Services > Sql Service Instance > Properties > Startup Parameters
3. Add the following statement: -T1222
4. Confirm the change by navigating to Advanced > Startup Parameters. This should be grayed out and display the new value that was added at the end with a delimited semicolon.