“REP-0004: Warning: Unable to open user preference file” while running reports.

“REP-0004: Warning: Unable to open user preference file” while running reports.
=*=*=*=*=* Error: REP-0004
Text: Warning - "Unable to open user preference file". while running reports.

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Cause:

Your local (customized) Oracle Reports preference file could not be opened.
This is just a warning, so the product will continue to run even if this occurs.
The possible causes of this error include the following:

Case 1: The file was not found under the specified name in the specified location.

Case 2: You lacked the necessary privileges to open the file.

Case 3: A system error made it impossible to open the file.

Action:

You can take the following actions to rectify this error:

Case 1: Make sure the file prefs.ora is located in your "home" directory.

Case 2: Make sure that you have the privileges necessary to access the file. If you don't, change your privileges accordingly.

Case 3: Consult your operating system documentation or contact your system administrator.

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The preferences file referred to above is:

Windows
ORACLE_HOME\CAUPREFS.ORA (user preferences)
ORACLE_HOME\CAGPREFS.ORA (global preferences)

UNIX
your_home_directory/prefs.ora (user preferences)
$ORACLE_HOME/tools/admin/prefs.ora (global preferences)

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Simple Way:

Check whether u have prefs.ora file in your application user's home

eg: prefs file should be in /home/applmg/prefs.ora

if not please copy prefs.ora file from  $ORACLE_HOME/tools/admin/prefs.ora  to /home/applmg/prefs.ora location.

Run your concurrent request/program.

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REP-0004: Warning: Unable to open user preference file

Metalink id:
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R12: Request Logs Contain the Message "REP-0004: Warning: Unable to open user preference file" [ID 1120529.1]

Symptoms:

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All concurrent requests that run REPORTS are printing the following warning in the request log.

REP-0004: Warning: Unable to open user preference file.

Cause:

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This message occurs when the concurrent process attempts to open the Oracle Reports executable and your local preference file cannot be found or opened. This is just a warning, so the request will continue to run even if this occurs.

Solution:

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To resolve the warning, copy the prefs.ora file from your Reports Builder $ORACLE_HOME/tools/admin/ directory into the Applications $HOME directory.

Example:

Copy of the file prefs.ora in the directory /u01/prod/apps/tech_st/10.1.2/tools/admin to the directory  /home/appprod/.

appdev@ctssd $ pwd
/u01/erpapp/10.1.2/tools/admin
appdev@ctssd $ cp prefs.ora /export/home/apptest

Note: Bounce apache service.

After doing above steps my issue resolved.