I am using oracle 11g. I noticed some performance problems that causes hanging on some search operations.
Can I still search based on an index while that index is being updated in the database?
Here is what the 11.2 Concepts Guide says about doing selects while dml is changing an index (ephasis mine):
So, you might see sightly degraded performance if you have a lot of indexes and a lot of DML taking place, but I suspect this is insufficient to cause the appearance of hanging. I suggest you trace a session to see what is slowing the search down.