Definition:
VALUE_ERROR exception (ORA-06502) occurs when an arithmetic, conversion, truncation, or size-constraint error occurs. For example, when a program selects a column value into a character variable, if the value is longer than the declared length of the variable, PL/SQL aborts the assignment and raises VALUE_ERROR. In procedural statements, VALUE_ERROR is raised if the conversion of a character string into a number fails. (Note that in SQL statements, INVALID_NUMBER is raised.)