While creating temporary tablespace one can create it by using datafile or tempfile but there is a big difference in performance using temp file will give you better performance since it is autimatically managed by oracle, once temp segment is inactive and nolonger in use oracle mark it that space available to others so it can be used by others. But when you use datafiles for temp tablespace smon has to drop inactive segments manually to release the space this is big overhead smon invokes to remove inactive temp segments periodically it may take upto 12 hrs of time so it unneccessarily raises requirement for bigger temporary tablespace. So better to always use tempfiles for temporary tablespaces