使用conn / as sysdba登录oracle，使用start mount出现此错误

sql> conn / as sysdba
Connected to an idle instance.
sql> startup mount;
ORACLE instance started.

Total System Global Area 4728872960 bytes
Fixed Size 1314156 bytes
Variable Size 163578516 bytes
Database Buffers 1019898880 bytes
Redo Buffers 6004736 bytes
Database mounted.
alter database open
*
ERROR at line 1:
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-00704: bootstrap process failure
ORA-00604: error occurred at recursive sql level 1
ORA-00942: table or view does not exist
Process ID: 2056
Session ID: 128 Serial number: 7


发现报的错和alert日志显示的一样。
这个错大概是system表空间里面的核心表被删除了，所以数据库启动不起来。这里，如果没有备份的话，这个就不能用常规的手段启动了。

首先去找到报ORA-00704的原因：
sql> conn / as sysdba
Connected to an idle instance.
sql> startup mount;
ORACLE instance started.

Total System Global Area 4728872960 bytes
Fixed Size 1314156 bytes
Variable Size 163578516 bytes
Database Buffers 1019898880 bytes
Redo Buffers 6004736 bytes
Database mounted.
sql> alter session set sql_trace=true;
sql> select value from v$diag_info where name='Default Trace File';

VALUE
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/iscba/iscba/trace/iscba_ora_22821.trc

sql> alter database open;
alter database open
*
ERROR at line 1:
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-00704: bootstrap process failure
ORA-00604: error occurred at recursive sql level 1
ORA-00942: table or view does not exist
Process ID: 2176
Session ID: 128 Serial number: 7

然后查看iscba_ora_22821.trc：

Trace file /u01/app/oracle/diag/rdbms/iscba/iscba/trace/iscba_ora_22821.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning,OLAP,Data Mining and Real Application Testing options
ORACLE_HOME = /u01/app/oracle/product/11.2/db_1
System name: Linux
Node name: h-badb-01
Release: 2.6.32-431.el6.x86_64
Version: #1 SMP Sun Nov 10 22:19:54 EST 2013
Machine: x86_64
VM name: VMWare Version: 6
Instance name: iscba
Redo thread mounted by this instance: 1
Oracle process number: 17
Unix process pid: 22821,image: oracle@h-badb-01 (TNS V1-V3)


*** 2016-02-25 10:41:03.622
*** SESSION ID:(202.3) 2016-02-25 10:41:03.622
*** CLIENT ID:() 2016-02-25 10:41:03.622
*** SERVICE NAME:() 2016-02-25 10:41:03.622
*** MODULE NAME:(sqlplus@h-badb-01 (TNS V1-V3)) 2016-02-25 10:41:03.622
*** ACTION NAME:() 2016-02-25 10:41:03.622

。。。省略N多字。

发现最后又如下提示：
=====================
PARSE ERROR #139799411328680:len=56 dep=1 uid=0 oct=3 lid=0 tim=1456368102317169 err=942
select order#,columns,types from access$ where d_obj#=:1
ORA-00704: bootstrap process failure
ORA-00604: error occurred at recursive sql level 1
ORA-00942: table or view does not exist
ORA-00704: bootstrap process failure
ORA-00604: error occurred at recursive sql level 1
ORA-00942: table or view does not exist

*** 2016-02-25 10:41:42.317
USER (ospid: 22821): terminating the instance due to error 704

*** 2016-02-25 10:41:43.413
EXEC #139799435394504:c=309952,e=2052517,p=57,cr=758,cu=0,mis=0,r=0,dep=0,og=1,plh=0,tim=1456368103413294
ERROR #139799435394504:err=1092 tim=1456368103413356

这个地方就能确定，是缺失 access$ 造成的数据库启动不起来。
为了解决问题，我们只有用非常规的手段来自己创建这个表，来进行恢复，步骤如下：
1.启动数据库到upgrade状态
sql> startup upgrade
ORACLE instance started.

Total System Global Area 4728872960 bytes
Fixed Size 1314156 bytes
Variable Size 163578516 bytes
Database Buffers 1019898880 bytes
Redo Buffers 6004736 bytes
Database mounted.
Database opened.

2.创建access$ 和相关的索引
sql> create table access$
2 ( d_obj# number not null,
3 order# number not null,
4 columns raw(126),
5 types number not null)
6 storage (initial 10k next 100k maxextents unlimited pctincrease 0)
7 /

Table created.

sql> create index i_access1 on
2 access$(d_obj#,order#)
3 storage (initial 10k next 100k maxextents unlimited pctincrease 0)
4 /

Index created.
注意：创建语句可以在$ORACLE_HOME/RDBMS/ADMIN/dcore.bsq中找到

3.重启数据库
QL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
sql> startup
ORACLE instance started.

Total System Global Area 4728872960 bytes
Fixed Size 1314156 bytes
Variable Size 163578516 bytes
Database Buffers 1019898880 bytes
Redo Buffers 6004736 bytes
Database mounted.
Database opened.

4.检查状态并用tnsname去连接 select status from v$instance; sqlplus username/password@TNSNAMES