Batch updates

Batch update support allows any updates to the database to be passed as a single transaction between the user program and the database. This procedure can significantly improve performance when many updates must be performed at once.

For example, if a large company requires its newly hired employees to start work on a Monday, this requirement makes it necessary to process many updates (in this case, insertions) to the employee database at one time. Creating a batch of updates and submitting them to the database as one unit can save you processing time.

There are two types of batch updates:

• Batch updates that use Statement objects.
• Batch updates that use PreparedStatement objects.

• Statement batch update
  To perform a Statement batch update, you must turn off auto-commit. In Java™ Database Connectivity (JDBC), auto-commit is on by default. Auto-commit means any updates to the database are committed after each SQL statement is processed. If you want to treat a group of statements being handed to the database as one functional group, you do not want the database committing each statement individually. If you do not turn off auto-commit and a statement in the middle of the batch fails, you cannot roll back the entire batch and try it again because half of the statements have been made final. Further, the additional work of committing each statement in a batch creates a lot of overhead.
• PreparedStatement batch update
  A preparedStatement batch is similar to the Statement batch; however, a preparedStatement batch always works off the same prepared statement, and you only change the parameters to that statement.
• BatchUpdateException
  An important consideration of batch updates is what action to take when a call to the executeBatch method fails. In this case, a new type of exception, called BatchUpdateException, is thrown. The BatchUpdateException is a subclass of SQLException and it allows you to call all the same methods you have always called to receive the message, the SQLState, and vendor code.
• Blocked insert support
  You can use a blocked insert is an iSeries™ operation to insert several rows into a database table at a time.