Did you try a Search using keywords dirty reads before posting? This post talks about enabling it in the database.
The Designer Database Specific FAQ (a Sticky at the top of the Semantic Layer forum) also mentions how to set a parameter for DB2 – maybe there’s such a way for SQL Server – you’d have to consult the database-specific user manual to see what your options are. (For me, it’s in the under C:\Program Files\Business Objects\Online Guides\EN\SybaseEN.pdf for version 5.1.9).
Anita Craig 
(BOB member since 2002-06-17)