I should have added that it's an 11g DB and we're using LMT tablespaces. On Friday, January 30, 2015 11:57 PM, Deepak Sharma <sharmakdeep_oracle@xxxxxxxxx> wrote: In order to resize a datafile to release space at the end, we need to find whatever the last block_id that is at the start of that free contiguous space. Problem is that we have a very large database such that querying dba_extents to find the last block is probably not an option. The standard query(ies) that make use of dba_extents runs for hours at stretch and also sometimes fails with a 'snapshot too old' (just gives up). Is there an alternative to using dba_extents? For example, if the datafile size is 100mb and the last 10mb is vacant, I want to know the block_id of where that 10mb begins.