http://download-west.oracle.com/docs...ts9a.htm#27571

Schema Object Naming Rules
Every database object has a name. In a SQL statement, you represent the name of an object with a quoted identifier or a nonquoted identifier.

A quoted identifier begins and ends with double quotation marks ("). If you name a schema object using a quoted identifier, then you must use the double quotation marks whenever you refer to that object.
A nonquoted identifier is not surrounded by any punctuation.
You can use either quoted or nonquoted identifiers to name any database object, with one exception: database links must be named with nonquoted identifiers. In addition, Oracle Corporation strongly recommends that you not use quotation marks to make usernames and passwords case sensitive.

See Also:
CREATE USER for additional rules for naming users and passwords


The following list of rules applies to both quoted and nonquoted identifiers unless otherwise indicated:

Names must be from 1 to 30 bytes long with these exceptions:
Names of databases are limited to 8 bytes.
Names of database links can be as long as 128 bytes.
Nonquoted identifiers cannot be Oracle reserved words. Quoted identifiers can be reserved words, although this is not recommended.

Depending on the Oracle product you plan to use to access a database object, names might be further restricted by other product-specific reserved words.