field normalization and omitNorms

[Phillip Farber]

Hi all,
I've been looking without success for a simple explanation of the effect 
of omitNorms=false for a text field. Can someone point me to the 
relevant doc?

What is the effect of omitNorms=false on index size and query 
performance for say 200K documents that have s single large text field 
that ranges from maybe 30K up to around 800K?  Do I want omitNorms=true 
or false?

Thanks!

Phil