This custom SQL string also sets up the environment, but the Integration Service runs the transaction environment SQL at the beginning of each transaction.
Use SQL commands that depend on a transaction being open during the entire read or write process. For example, you might use the following statement as transaction environment SQL to modify how the session handles characters:
ALTER SESSION SET NLS_LENGTH_SEMANTICS=CHAR
This command must be run before each transaction. The command is not appropriate for connection environment SQL because setting the parameter once for each connection is not sufficient.