Oracle 11g Rel 2 :- Question on Index usage

What will be the overhead on turning on usage monitoring on all the 120k + indexes in an OLTP with heavy select transactions?
Will that can be a performance bottleneck ?
We are in the process of dropping unused indexes so need to know which indexes are not at-all used. Is there some better way to get the result?
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the overhead is very little
but, it is non-zero.

You probably won't notice but without knowing your exact usage profile, can't say for sure.

Unfortunately, monitoring simply flips a flag.   So, it'll work great for things used often as they will get the "Yes" flag turned on immediately.

Indexes that are used less frequently but are still important will appear unused, but that doesn't mean you don't need them.

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slightwv (䄆 Netminder) Commented:
>> need to know which indexes are not at-all used.

Even though this was commented on above, I wanted to state it differently:
How are you going to determine "unused"?  

I realize this is by "monitoring" but how long are you going to monitor before you label it "unused"?

An example:
An index might only be necessary for an end-of-year closeout.  With the index, a closing might take 10 hours.  Without the index, it might take 48 hours.

What about other batch type processing that happens say, monthly, quarterly, etc...?
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