Keyword and Parameter Description:
This is an undeclared identifier which optionally labels the PL/SQL block. When used, label_name should be enclosed by the double angle brackets and should appear at the beginning of the block. Optionally, label_name can also become visible at the end of the block.
The global identifier declared in an enclosing block can be re-declared in a sub-block, in that case the local declaration prevails and the sub-block cannot reference the global identifier. To reference the global identifier, you should use the block label to qualify the reference, as the illustration below shows:
IF x = outer.x THEN -- refers to global x