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Don Burleson Blog 







nls_length_semantics tips

Oracle Database Tips by Donald BurlesonMay 20, 2016

Question: What does the nls_length_semantics parameter do?  Can you show an example using nls_length_semantics?

Answer:  The nls_length_semantics parameter enables you to create CHAR and VARCHAR2 columns, using either byte or character length semantics. The default for nls_length_semantics is "byte". You MUST create a new database with nls_length_semantics=byte because scripts such as catalog.sql must use the byte setting.

Oracle notes this about the nls_length_semantics parameter:

"The session-level value of nls_length_semantics specifies the default length semantics to use for VARCHAR2 and CHAR table columns . . .

This default may be overridden by the explicit length semantics qualifiers BYTE and CHAR in column, attribute, and variable definitions.

The instance-level value of nls_length_semantics provides a default for the session-level value if nls_length_semantics it is not set explicitly by the database client through the nls_length_semantics client environment variable (does not apply to JDBC Thin clients, or the ALTER SESSION SET nls_length_semantics statement."

WARNING:  Oracle strongly recommends that you NOT set NLS_LENGTH_SEMANTICS=CHAR in the init.ora or spfile. Doing this may cause many existing installation scripts to unexpectedly create columns with character length semantics, resulting in runtime errors, including buffer overflows.

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