Hi, and welcome to LQ!
I don't think that this task is common enough for anyone to have written
a utility for it. Your specs are a bit thin, too. Oracle (which version
are you using, btw?) has built-in features that allow execution of code
at given times (similar to cron). You can write an Oracle Perl script
that reads /etc/passwd and updates a table. ... there's more than one
way to skin this cat.