No reads of aborted transactions. Maintains table of locks for data items for a server. Two transactions are waiting and dependent on the other to release a lock so they can resume. V Checked periodically or each time edge is added. If deadlock detected, select transaction to abort.
Reads occur immediately.
Writes record new values in work area. Records kept of all data items read and written to. Ti Write then Tj Read. Ti Write then Tj Write. All tentative changes are made permanent.