NLS_LENGTH_SEMANTICS

Parameter type	String
Syntax	NLS_LENGTH_SEMANTICS = string Example: NLS_LENGTH_SEMANTICS = 'CHAR'
Default value	BYTE
Parameter class	Dynamic: ALTER SESSION, ALTER SYSTEM
Range of values	BYTE | CHAR

NLS_LENGTH_SEMANTICS enables you to create CHAR and VARCHAR2 columns using either byte or character length semantics. Existing columns are not affected.

Databases should use byte semantics rather than character semantics if they have a variable-width multibyte character set. All other databases should be created or eventually migrated to character semantics. Old databases using unmodified old applications should use byte semantics.

NLS_LENGTH_SEMANTICS does not apply to tables in SYS and SYSTEM. The data dictionary will always use byte semantics regardless. Also, NCHAR, NVARCHAR, CLOB, and NCLOB are always character-based.