Function purity levels define what type of data structures can be read or modified by a function. There are four function purity levels, which are given as follows:
? WNDS — Writes no database state. The function does not modify any database table using any DML statement.
? RNDS— Reads no database state. The function does not read any database tables using the SELECT statement.
? WNPS — Writes no package state. The function does not modify any packaged variables.
? RNPS— Reads no package state. The function does not read any packaged variables.
? WNDS — Writes no database state. The function does not modify any database table using any DML statement.
? RNDS— Reads no database state. The function does not read any database tables using the SELECT statement.
? WNPS — Writes no package state. The function does not modify any packaged variables.
? RNPS— Reads no package state. The function does not read any packaged variables.