Query to monitor the temp total, used and free space in mb:
Select A.tablespace_name tablespace , D.mb_total, SUM(A.used_blocks * D.block_size) / 1024 / 1024 mb_used, D.mb_total - SUM(A.used_blocks * D.block_size) / 1024 / 1024 mb_free
From v$sort_segment A, ( select B.name, C.block_size, SUM(C.bytes) / 1024 / 1024 mb_total from v$tablespace B, v$tempfile C where B.ts#= C.ts#
Group by B.name, C.block_size) D
Where A.tablespace_name = D.name
Group by A.tablespace_name, D.mb_total
Query to Resize the temp file space:
Alter Database TEMPFILE 'tempfile' RESIZE 300G