restore UNDO tablespace from RMAN
[oracle@shiven instance]$ sqlplus sys/sys as sysdba SQL*Plus: Release 11.2.0.2.0 Production on Tue Jun 3 11:01:08 2014 Copyright (c) 1982, 2010, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> archive log list; Database log mode No Archive Mode Automatic archival Disabled Archive destination /data1/shiven01/dbs/arch Oldest online log sequence 1 Current log sequence 3 SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount ORACLE instance started. Total System Global Area 535662592 bytes Fixed Size 1345376 bytes Variable Size 163580064 bytes Database Buffers 364904448 bytes Redo Buffers 5832704 bytes Database mounted. SQL> alter database