ORA-29855 error in oracle and solution

We sometime see the error when insufficient privileges are assigned and CTXSYS is not presented in oracle db 10g.

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.TEXTINDEXMETHODS", line 364

This errors comes when lack of privileges/roles when we work with text components (formerly known as Context, or Intermedia Text), this concept provides a powerful search, retrieval, and viewing capabilities for text stored in oracle database.

The solution is as follows:
AS sys DBA:
GRANT EXECUTE ON CTX_DDL TO username ; -- for oracle text package execution i.e. index rebuild and synchronize etc. Ignore if CTX_DDL not going to be used.
grant CTXAPP to username ;

Solution:
-----------
Ensure that CTXSYS schema is installed on database instance.

Install:
@? points oracle home directory i.e. ORACLE_HOME variable, ensure ORACLE_HOME and ORACLE_SID is set (window) or with export in UNIX.
The steps to be executed as SYS user
create tablespace drsys as sysdba
run @?/ctx/admin/catctx.sql ctxsys drsys temp01 nolock
run @?/ctx/admin/defaults/drdefus.sql (as CTXSYS user )-- see below for why and how
grant execute on ctxsys.ctx_ddl to user;

Uninstall:
@?/ctx/admin/catnoctx.sql as sys

The next step is to install appropriate language-specific default preferences. There is script which creates language-specific default preferences for every language Oracle text supports in ORACLE_HOME/ctx/admin/defaults directory and script should be executed as CTXSYS user.
@?/ctx/admin/defaults/drdefXX.sql -where XX is the language code


- wish this helps you too..