DB2

At the beginning of a transaction Cúram obtains a single connection to the database. This connection runs at a specific isolation level:

• Repeatable Read - This guarantees that dirty data is not read and that a second read will read the same thing as a first.

However specific categories of statements are run at a lower isolation level:

• Cursor Stability - Cursor stability is the DB2 implementation of the SQL standard Read Committed isolation level. This guarantees that a transaction cannot read a row with uncommitted changes in it. However it does not guarantee that a second read will read the same thing as a first.

This is not a separate connection to the database rather the DB2 keyword WITH CS is automatically appended to the SELECT statement.

All queries which do not have the forUpdate flag set run at the "Cursor Stability" isolation level. All modifies and queries with the forUpdate flag set run at "repeatable read" isolation level. This means that they place a lock on the row(s) that have been read so that they cannot be updated by anyone else, and in the case of modify operations be read by anyone else. This lock is not released until the transaction commits.