A manual master dataset works differently from an automatic master. But suppose that one of our clerks miskeyed the account number and entered YY-123 instead. Manual Masters are appropriate when the master contains a record for every possible valid key. For example, your application may allow only a certain number of predefined valid part numbers or account numbers. If you don't want to create a new record just because some clerk miskeyed something, then you should be using manual masters, because errors will be rejected automatically.
Automatic masters make sense for more free-form kinds of keys.
Dates are frequently associated with automatic masters, because you don't need a table to determine whether a date is valid or not. For example, look at the schema shown in Figure 2 . Finally, every schema ends with the word END followed by a period. This program is in PUB.SYS and is bundled with every HP 3000. Most of these errors are pretty easy to understand.