create text index error

Error starting AT line : 1 IN command -
CREATE INDEX MM_CATALOG_SEARCH_IDX1 ON MM_CATALOG_ITEM_SEARCH_T (CATALOG_DESC)
        indextype IS ctxsys.ctxcat
Error AT Command Line : 1 Column : 14
Error report -
SQL Error: ORA-29855: error occurred IN the execution OF ODCIINDEXCREATE routine
ORA-20000: Oracle Text error:
DRG-10700: preference does NOT exist: CTXSYS.DEFAULT_LEXER
ORA-06512: AT "CTXSYS.DRUE", line 160
ORA-06512: AT "CTXSYS.CATINDEXMETHODS", line 98
29855. 00000 -  "error occurred in the execution of ODCIINDEXCREATE routine"
*Cause:    Failed TO successfully EXECUTE the ODCIIndexCreate routine.
*Action:   CHECK TO see IF the routine has been coded correctly.