increase size of tmp directory when execute delete query

Query to delete data from a table of about 15 GB.
SQL> delete from test_log_hist where SEQ < 8302000;

/tmp size increased to 21% when performing delete query.
/dev/sda7 20961280 4367932 16593348 21% /MARIA_TMP

I wonder why you use/tmp area
Please tell me how to process the delete query