This error only occurs on custom forms whereas it does not throw any error for standard forms.

I checked the form related AOL objects as below.

Responsibility: Order Management Super User

Menu: ONT_SUPER_USER

Function: *** Notebook

Form: **** Notebook

The AOL objects seem to be absolutely ok.

What is the reason for this error?

The reason for this issue is that and entry is missing for the CUSTOM_TOP in default.env file. In R12 the CUSTOM_TOP should be defined in default.env located at $INST_TOP/ora/10.1.2/forms/server directory.

Solution 

1. Login to Linux server with APPLMGR manager user access.

2. Modify default.env file.

Ensure that your CUSTOM_TOP’s are registered in the default.env file.

This means there should be an entry for environment variable CUSTOM_TOP (which contains physical path to your custom directory).default.env file is present at,

$INST_TOP/ora/10.1.2/forms/server directory, in Unix.

For Example:

APPL_TOP=/home/applmgr/PROD/apps/apps_st/appl

CUSTOM_TOP=/home/applmgr/PROD/apps/apps_st/custom

3. Restart the middle tier services.

4. Retest the issue.

The solution is illustrated below

Step 1: Modify default.env

Go to the following directory, $INST_TOP/ora/10.1.2/forms/server. Check for the file named, default.env.

Open the file, default.env

Search for the corresponding custom top. In our case we need to find the entry for the custom top, FCA_TOP.

We got the message that there is no entry for FCA_TOP. Scroll down to the bottom of the file where all the top directories are mapped to the physical directories

Now we shall add the entry for FCA_TOP at the end

The entry should be like the following,

CUSTOM_TOP=/home/applmgr/PROD/apps/apps_st/custom

Save the file.

Step 2: Bounce Apps server

Bounce the apps web server as given in the following article.

Step 3: Retest the issue

Now try to open the custom form from the front end.

The custom form opens successfully. Problem is solved.