Function Purity Level

The function purity level defines what structures the function reads or modifies.
Purity levels

• WNDS - Writes No Database State i.e. Function does not modify any database tables (No DML)
• RNDS - Reads No Database State i.e. Function does not read any tables (No select)
• WNPS - Writes No Package State i.e. Function does not modify any packaged variables (packaged variables are variables declared in a package specification)
• RNPS - Reads No Package State i.e. Function does not read any packaged variables

Syntax:

PRAGMA RESTRICT_REFERENCES (function_name, WNDS [, WNPS] [, RNDS] [, RNPS])

Tells the compiler the purity level you believe your function meets or exceeds