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 partitions of which reside in read-only tablespaces, which is illegal
ensure that value of INITRANS (whether specified explcitly or derived from the default value for the partitioned table or index) is no greater than that of MAXTRANS
Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e12700.htm
https://community.oracle.com/message/3229900
Browse all solutions to database errors from Oracle, MS SQL, or MySQL