What methods can ensure transaction isolation in database management systems?

Transaction isolation in DBMS is achieved through isolation levels, which determine how and when changes made by one transaction become visible to others. The main methods of ensuring isolation:

• Transaction Isolation Levels (ANSI SQL standards):

  • Read Uncommitted — the lowest isolation level, allows "dirty reads".
  • Read Committed — prevents dirty reads but allows non-repeatable reads.
  • Repeatable Read — prevents non-repeatable reads but allows phantom reads.
  • Serializable — the strictest, provides full isolation as if transactions were executed sequentially.

• Locks:

  • Locks at row, table, or page level to prevent concurrent access.
  • Can be exclusive (for writing) or shared (for reading).

• MVCC (Multiversion Concurrency Control) mechanisms:

  • Allows transactions to work with different versions of data, reducing locking.

• Use of transactional managers and settings in JDBC:

  • In Java, you can set the isolation level via Connection.setTransactionIsolation().

Example of setting the isolation level in Java:

connection.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);