Question

Whats the worst that can happen if I drop existing indexes in SQL Server 2000 (and are the effects similar in 2008 R2?)?

I understand it may slow down some queries, but is that the worst thing that can happen?

I’m looking at the Index Tuning Wizard and trying to decide if I need to keep all existing indexes or not because what if the past DBAs applied the wrong ones? What should I do if the tuning wizard gives me a much higher improvement % with keeping existing turned off?

Answer 1

• slow down, sometimes dramatically
• dropping unique indexes can cause to data unconsistancy and thus – wrong query results
• dropping indexes on calculated columns – can even more dramatically reduce performance
• increases usage of buffer pool – thus may be denial of servicing some memory loading CLR code or even regular queries. Due to lack of memory can cause more often recompilations
• can cause many more deadlocks
• can heavily increase pressure to IO subsystem