The fun with names and PLS-00302

Quite often it turns out that the more mysterious the problem is the more trivial is the solution.
This is a short note about such a situation.

There is a package, which prepares a report. The package has the VALID status, no problems with the compilation or so. However, the call to the procedure ended with throwing the exception PLS-00302 (component zzz must be declared). The call from the owner schema, so not problems with the visibility of the package, the DESCRIBE command works as expected.
To make the long story short I found out that the exception had been risen, when the call was fully qualified with the schema name. If there was no schema specification, the code had been working properly. The reason was the existence of another package with the same name as the schema name, and the problem was with the context resolution - in the first place there was a search within the package and not within the schema namespace.

The workaround is simple - not to call the package prefixed with the schema name. The true solution is clear (though not necessarily simple due to possible dependencies) - to change the package name to different than the schema name and of course to avoid naming the packages with names of schemas.