SQL> create table t (v integer);

Table created.

SQL> create materialized view log on t with rowid;

Materialized view log created.

SQL> desc MLOG$_T  
 Name                             Null?    Type
 -------------------------------- -------- ----------------------
 M_ROW$$                                   VARCHAR2(255 CHAR)
 SNAPTIME$$                                DATE
 DMLTYPE$$                                 VARCHAR2(1 CHAR)
 OLD_NEW$$                                 VARCHAR2(1 CHAR)
 CHANGE_VECTOR$$                           RAW(255)