Linked Oracle table query gets much slower when returning much less data

[projecttoday]

I have an Access database which is reading tables in an Oracle database using linked tables and pass-through queries. I have one query that has me puzzled. It has a WHERE clause that selects from a table based on one column being greater than a specified numeric value. The thing is when I use a value that returns most of the records in the table, it runs way faster than when I use a value that returns a small fraction of the total records.

The only thing different between the 2 cases is I'm changing this constant value in the query. This happens with both a linked-table version of the query and a pass-through version of the query. The almost-all records takes a few seconds to return its results while the restricted select takes 8 minutes or more. Can anybody shed some light as to why this works this way?

 

[spikepl]

Is that field indexed?

 

[jdraw]

Can you post the sql?

 

[projecttoday]

Everything seems to be working fast this morning. I'll get back later when it starts happening again, which I'm sure it will. Thanks for looking.