This Oracle tutorial explains how to use the Oracle/PLSQL VSIZE function.
The Oracle/PLSQL VSIZE function returns the number of bytes in the internal representation of an expression.
VSIZE
returns the storage size of a string in Oracle.
The general format for this function is:
VSIZE(string)
SQL> SELECT VSIZE('a string') FROM dual;
VSIZE('ASTRING')
----------------
8
SQL>