undo损坏后的修复分为以下三种情况：
一、数据库正常关闭immediate或normal ①、创建pfile并使用pfile启动数据库 startup nomount create pfile=<path> from spfile; shutdown abort startup mount restrict pfile=<path> ②、尝试恢复文件 select name,file#,status from v$datafile; recover datafile <file#或name>; ③、创建新的undo表空间替换损坏的undo表空间 alter database datafile <file#> offline drop; alter database open; CREATE UNDO TABLESPACE UNDOTBS2 DATAFILE '<path>' SIZE 10M AUTOEXTEND ON RETENTION NOGUARANTEE; shutdown immediate; ④、修改pfile: undotablespace=UNDOTBS2 ⑤、删除损坏undo表空间并创建新的SPFILE startup pfile=<pfile_path> drop tablespace UNDOTBS1 including contents and datafile; create spfile from pfile='<pfile_path>'shshutdown immediate startup 二、abort或crash ①、创建pfile startup nomount create pfile=<path> from spfile; ②、修改pfile undo_tablespace='SYSTEM' undo_management='MANUAL' *._allow_resetlogs_corruption=true （注：允许在数据库文件SCN不一致的情况下启动数据库） *._corrupted_rollback_segments=(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,_SYSSMU4$,_SYSSMU5$,_SYSSMU6$,_SYSSMU7$,_SYSSMU8$,_SYSSMU9$,_SYSSMU10$) （注：允许在rollback segments损坏的情况下启动数据库） (注：rollback的名称要与已经损坏的undo表空间的rollback segment号保持一致，不然导致无法删除损坏的undo表空间） ③、使用修改后pfile启动数据库 startup mount restrict pfile='<pfile_path>' ④、修改损坏数据文件状态 select name,file#,status from v$datafile; alter database datafile <file#> offline drop; ④、打开数据库 alter database open; ⑤、并创建新的undo表空间并关闭数据库 CREATE UNDO TABLESPACE UNDOTBS2 DATAFILE '<path>' SIZE 10M AUTOEXTEND ON RETENTION NOGUARANTEE; shutdown immediate; ⑥、修改pfile undo_tablespace='UNDOTBS2' undo_management='AUTO' ⑦、启动数据库并删除损坏undo表空间 startup restrict pfile=<pfile_path> 修改损坏undo表空间状态 alter tablespace undotbs1 offline immediate; 删除损坏undo表空 drop tablespace UNDOTBS1 including contents and datafile;三、online ①、创建新的undo表空间 CREATE UNDO TABLESPACE UNDOTBS2 DATAFILE '<path>' SIZE 10M AUTOEXTEND ON RETENTION NOGUARANTEE; ②、改变默认undo表空间 ALTER SYSTEM SET UNDO_TABLESPACE='<new undo tablepace name>'; ③、删除损坏undo表空间 DROP TABLESPACE <old undo tablespace name> INCLUDING CONTENTS AND DATAFILE;四、相关视图： v$datafile v$rollname v$rollstat v$tablespace dba_rollback_segs dba_data_files dba_talbespaces dba_segments
