PL/SQL Identifiers

Identifiers are names for PL/SQL objects such as constants,variables, exceptions, procedures, cursors, and reserved words.

Identifiers have the following characteristics:
• Can be up to 30 characters in length
• Cannot include whitespace (space, tab, carriage return)
• Must start with a letter
• Can include a dollar sign ($), an underscore (_), and a
pound sign (#)
• Are not case-sensitive

You shouln't use the  PL/SQL’s reserved words as identifiers in your programs as this can result in compilation or runtime errors that are difficult to troubleshoot.