本人一次碰到有人将数据库DBA ROLE删除掉了，惊奇之余 ,只好想办法恢复，经查找资料，终于完全恢复了DBA ROLE，现将恢复过程与大家共享：
用 sys/xxxx as sysdba登录sqlplus，然后执行下列语句：
SQL> create role dba;
SQL> grant all PRivileges to dba with admin option;
SQL> grant select_catalog_role to dba with admin option;
SQL> grant execute_catalog_role to dba with admin option;
SQL> grant delete_catalog_role to dba with admin option;
EXPlanation:
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The DBA role is created at database creation time by the "sql.bsq" script. (The "sql.bsq" script is typically found in the $Oracle_HOME/dbs or the
$ORACLE_HOME/rdbms/admin Directory.)
Additional grants are made to dba through other scripts in the admin directory.
For example, exp_full_database and imp_full_database in catexp.sql.
The above commands are excerpts from the "sql.bsq" script