Directory defined by $APPLPTMP & $APPLTMP

Oracle Doc ID 1355735.1 (Difference between APPLPTMP and APPLTMP Directories in EBS) tells the difference between APPLPTMP and APPLTMP Directories in EBS. Here is more info on troubleshooting. 

  

- Variable $APPLPTMP is defined on EBS apps server, but the directory does not have to exist on the apps forms/web server.

Instead, the directory has to exist on the database server. Otherwise, below error will show up in CM program log. I also saw similar error when the folder has too many files.

ORACLE error 20100 in FDPSTP
Cause: FDPSTP failed due to ORA-20100: File o0275459.tmp creation for FND_FILE filed.
You will find more information on the cause of the error in request log.
ORA-06512: at "APPS.FND_FILE", line 410
ORA-06512

And, make sure the directory is part of the database parameter utl_file_dir:
SQL> select name, value from v$parameter where name = 'utl_file_dir';

To test its setup, run
SQL> exec FND_FILE.PUT_LINE(fnd_file.log, 'Hello World!');
A new file with a name like l000xxxx.tmp is created in the first directory in the db parameter utl_file_dir, containing 'Hello World!'. 

UPDATE: *warning* In 12c database, after above statement, it needs to run CLOSE line. Otherwise the log file size may be 0!
SQL> exec fnd_file.close;

Below line will work but will not create a file o000xxxx.tmp and write one line to it until CLOSE line was run.

SQL> exec FND_FILE.PUT_LINE(fnd_file.output, 'Hello output!');

SQL> exec fnd_file.close;

- Variable $APPLTMP is the location to save temporary files from forms run-time on the forms/web server. A cron job can be scheduled to delete old files in that directory.
One day, server experienced files filling up $APPLTMP quickly with files in 2GB size:
-rw-r----- 1 user1 users 2147483647 Feb 4 07:12 OFN6pYCK.t
-rw-r----- 1 user1 users 2147483647 Feb 4 07:16 OFNF0HJf.t
-rw-r----- 1 user1 users 2007334912 Feb 4 07:39 OFVuhSzG.t

The file holds entries of hours earlier than the file's timestamp:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Subledger Accounting: Version : 12.0.0
Copyright (c) 1979, 1999, Oracle Corporation. All rights reserved.
XLAACCUP module: Accounting Program
+---------------------------------------------------------------------------+
Current system time is 04-FEB-20XX 01:02:47 
... ... ...

I found debug log was turned on by "FND: Debug Log Enabled =Yes" on site level. So, make sure below settings are off in Profile options:

FND: Debug Log Enabled = No
SLA: Enable Diagnostics = No
AR: Enable Debug Message Output = No

- Variable s_forms_tmpdir in CONTEXT_FILE also defines a location holding forms temp files.
On a busy day, Sys Admin saw /tmp was almost full by 7 GB file /tmp/file75jBt9.TMP, while EBS R12 variable s_forms_tmpdir sets to /tmp directory. Even this file was marked "deleted", the space was not released as long as a frmweb / forms session had it open by a user who was extracting a large portion of year-end data.

UPDATE in Sept 2022:

Starting in Oracle Database 18c, parameter UTL_FILE_DIR is no longer supported. Instead, specify the name of a directory object. 

Since the UTL_FILE_DIR initialization parameter is deprecated, it is no longer listed in V$SYSTEM_PARAMETER and related views:

SQL> SELECT value FROM v$system_parameter WHERE name='utl_file_dir' ;

no rows selected

SQL> SELECT value FROM v$parameter WHERE name='utl_file_dir' ;

VALUE

--------------------------------------------------------------------------------

/path/to/utl_dir,/home/u01/app/oracle/product/19.0.0.0/temp/EBSDEV

And, it can not be altered at DB level:

SQL> alter system set utl_file_dir='/path/to/utl_dir';