Log File, Dead Lock, Data Item.

1. Definition of log file with explanatin
2. Why prevention in deadlock handling is not always possible ?
3. Explain the version of data item with example.

1. A log file is a recording of everything that goes in and out of a database. The alert log file (also referred to as the ALERT.LOG) is a chronological log of messages and errors written out by an Oracle Database. 
2. Prevention in deadlock handling is not always possible because deadlocks are not detected properly.
3. Dear student data item is nothing but the data user inserted into the database.