ORA-20100: Error: FND_FILE FAILURE unable to create file in the directory,/usr/tmp.

Concurrent requests are failed with the below error:

ORA-20100: Error: FND_FILE failure. Unable to create file, o0040178.tmp in thedirectory, /usr/tmp.

You will find more information in the request log.
ORA-06512: at "APPS.FND_FILE", line 417
ORA-06512: at "APPS.FND_FILE", line 456
ORA-06512: at line 1

Upon checking below settings there is no issue :

1. The $APPLTMP, $APPLPTMP variables and UTL_FILE_DIR database parameter are valid and pointing to directory where there is enough space and users have written permission.
2. FND_FILE.PUT_LINE is able to create new files in the temporary directory.

FND_FILE.PUT_LINE Checking method:

SQL> exec FND_FILE.PUT_LINE(FND_FILE.LOG, 'THIS IS A TEST');

This should dump a file on APPLPTMP. If this test works, it would indicate that FND_FILE is ok and the problem is possibly with the Application.

You may want to leave only one entry on utl_file_dir for this test.

finally I checked the utl_file_dir, but there is no entry like /usr/tmp path in that list

SQL> connect / as sysdbaSQL> show parameter UTL_FILE_DIR

just I added /usr/tmp for the UTL_FILE_DIR & restarted the applications & database.

now the issue is resolved & concurrent requests are working fine