LOGIN PAGE appears blank in Oracle Applications R12

Issue:
When logging onto E-Business Suite front end page, the login page appears blank and nothing loads; – Unable to access login Page in Oracle APPS R12

Temporary Fix:
1. Shutdown the application services
2. Compile the jsp’s manually using the below command
perl $FND_TOP/patch/115/bin/ojspCompile.pl –compile –flush -p 2
3. Restart the application services
4. Retest the issue.

Permanent Fix:
1. Set the parameter “s_jsp_main_mode” in XML file from “just run” to “recompile”
<jsp_debug_parameters oa_var=”s_jsp_main_mode”>justrun</jsp_debug_parameters>
change it to  <jsp_debug_parameters oa_var=”s_jsp_main_mode”>recompile</jsp_debug_parameters>

2. Execute autoconfig to apply the change done in XML File. Autoconfig will update file $INST_TOP/ora/10.1.3/j2ee/oacore/application-deployments/oacore/html/orion-web.xml

3. Re-start the applications and test the issue.

Note: However it is not recommended to change the default value of parameter s_jsp_main_mode (i.e. just run) as it may lead to performance issue.

Cause:
Issue is caused by missing class files on the OA_HTML directory.

References:
Note: Oracle E-Business Suite R12 – Login Page showing a blank page Occuring Intermittently [ID 1491845.1]