oracle 10g 启动过程，输入alter database mount后出现2，求指教~

SQL> startup nomount
ORACLE 例程已经启动。Total System Global Area 1694498816 bytes
Fixed Size                  1293408 bytes
Variable Size             637535136 bytes
Database Buffers         1048576000 bytes
Redo Buffers                7094272 bytes
SQL> alter database mount
  2
这个启动过程中的第二步，输入alter database mount后，回车出现个2，求解！