You can use lsof to identify the form process that is creating a big file:
$ lsof /tmp
frmweb 17530 applmgr 51u REG 253,3 364544 6832 /tmp/file9ogKcF.TMP (deleted)
The one shown above is fairly a small tmp file. Following steps would help to change the form temporary file directory a different one. I use linux/Unix machines for the system.
1. Request your sysadmin/UX team to give you a new mount point. It is encouraged to have local filesystem. For example: /frmtemp . Do make sure applmgr or your oracle EBS owner have privileges to write files to the mount point.
2. Update the TMPDIR environment variable in the file - $INST_TOP/ora/10.1.2/forms/server/default.env
TMPDIR=/frmtemp
3. Restart forms using adformsctl.sh stop/start. The script is located at $ADMIN_SCRIPTS_HOME.
Once done, you can check for tmp files getting created in /frmtemp.
4. The above 3 steps will be over written if any DBA executed an autoconfig. It is a good practice to make changes in the context file.
Location of the context file: $INST_TOP/appl/admin
Edit the (s_forms_tmpdir) parameter in the context file to reflect /frmtemp.