We cannot use following command to move Oracle context index to another tablespace, because it's a special kind of index.
ALTER INDEX ... REBUILD TABLESPACE CTXDATA;
You need create new storage setting or modify existing storage setting. Following is to create a new one.
begin
ctx_ddl.create_preference('CTXSTORE', 'BASIC_STORAGE');
ctx_ddl.set_attribute('CTXSTORE', 'I_TABLE_CLAUSE', 'tablespace CTXDATA');
ctx_ddl.set_attribute('CTXSTORE', 'K_TABLE_CLAUSE', 'tablespace CTXDATA');
ctx_ddl.set_attribute('CTXSTORE', 'R_TABLE_CLAUSE', 'tablespace CTXDATA');
ctx_ddl.set_attribute('CTXSTORE', 'N_TABLE_CLAUSE', 'tablespace CTXDATA');
ctx_ddl.set_attribute('CTXSTORE', 'I_INDEX_CLAUSE', 'tablespace CTXDATA');
ctx_ddl.set_attribute('CTXSTORE', 'P_TABLE_CLAUSE', 'tablespace CTXDATA');
end;
/
Then you can run the following command to rebuild the Oracle context index.
ALTER INDEX ... REBUILD PARAMETERS 'REPLACE STORAGE CTXDATA';
Then check the space usage of the tablespace.