Cause: User issued ALTER TABLE statement attempting to modify an existing VARCHAR2 (or VARCHAR) column to be of type CHAR (or CHARACTER), increase length of an existing CHAR (or CHARACTER) column, or add a column with user-specified default for a table one or more subpartitions of which reside in read-only tablespaces, which is illegal See the solution below.

Error solution: Avoid performing aformentioned operations on a partitioned table one or more subpartitions of which reside in read-only tablespaces