The Concept of Transaction Processing
Properties of Transactions
Basic operations are read and write
Concurrency control
Transaction Recovery
Transaction states.
Transaction and System Concepts
Recovery techniques
The System Log:
Commit Point of a Transaction:
Transaction Schedules based on Recovery & Serializability
Transaction Support in SQL
Database Concurrency Control
Database Concurrency Control(Dealing with Deadlock)
Assignment no. 5

Commit Point of a Transaction:

Commit Point of a Transaction:
Definition: A transaction T reaches its commit point when all its operations that access the database have been executed successfully and the effect of all the transaction operations on the database has been recorded in the log. Beyond the commit point, the transaction is said to be committed, and its effect is assumed to be permanently recorded in the database. The transaction then writes an entry [commit,T] into the log.
Roll Back of transactions: Needed for transactions that have a [start_transaction,T] entry into the log but no commit entry [commit,T] into the log.
Redoing transactions: Transactions that have written their commit entry in the log must also have recorded all their write operations in the log; otherwise they would not be committed, so their effect on the database can be redone from the log entries.
Force writing a log: before a transaction reaches its commit point, any portion of the log that has not been written to the disk yet must now be written to the disk. This process is called force-writing the log file before committing a transaction.