Cause: When you ALTER DATABASE ... CHARACTER SET, the new character set must be a superset of the old character set. For example, WE8ISO8859P1 is not a superset of the WE8DEC.

Action: Specify a superset character set.

Cause: When character set conversion happens between CHAR and NCHAR either implicitly or explicitly, some characters are lost due to no mapping characters in the destination character set.

Action: Make sure all the characters can be mapped to destination character set or set NLS_NCHAR_CONV_EXCP to be FALSE.

Cause: Only UTF8 and AL16UTF16 are allowed to be used as the national character set

Action: Ensure that the specified national character set is valid

Cause: The character set specified is not allowed for this operation or is invalid

Action: Ensure that the specified character set is valid

Cause: CLOB data changes representation to Unicode when converting to a multibyte character set and must be migrated

Action: Remove CLOB data as listed in the alert file. CLOB data can be migrated by methods such as import/export

Cause: NCLOB, NCHAR or NVARCHAR2 data changed the representation to Unicode when converting to a multibyte character set and must be migrated.

Action: Remove NCLOB, NCHAR or NVARCHAR2 data as listed in the alert file. The above type data can be migrated by methods such as import/export.