On a recent installation we had problems serving APEX static files (application and workspace), they would always report a 404 not found back from ORDS.
Of course I checked all required DB users and the ORDS config files, but couldn’t find anything obvious. Also no REST service defined in APEX would work.
By looking into the tomcat logfile I found a strange error:
WARNING: ORA-04063: view "ORDS_METADATA.UNIFIED_POOL_CONFIG" has errors
with a whole Java Exception stack behind it.
At some other place in the logfile ORDS actually recommends what to do:
Please run the following command and restart Oracle REST Data Services: java -jar ords.war validate --database apex
And then I realized what happened: I had APEX 18.1 and ORDS 18.2 installed on this server, but then reverted back to APEX 5.1.4. Of course we need to tell ORDS that something changed.
So after running java -jar ords.war validate –database apex and restarting tomcat everything worked just fine.
This just shows how important it is to actually read logfiles.