重建smon_scn_time表和索引

参考文章：http://www.cndba.cn/dave/article/1975；http://www.cndba.cn/dave/article/1285

smon_scan_time表介绍：scn和时间的对应关系表，由smon进程维护
scn：系统改变数字，保证数据一致性

一、创建SMON_SCN_TIME表

先对SMON_SCN_TIME进行查询，和表中的记录内同

SQL> desc smon_scn_time
Name                       Null?    Type
----------------------------------------- -------- ----------------------------
THREAD                         NUMBER
TIME_MP                        NUMBER
TIME_DP                        DATE
SCN_WRP                        NUMBER
SCN_BAS                        NUMBER
NUM_MAPPINGS                        NUMBER
TIM_SCN_MAP                        RAW(1200)
SCN                            NUMBER
ORIG_THREAD                        NUMBER
SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';
Session altered.
SQL> select time_dp,scn from smon_scn_time where rownum<5;
TIME_DP            SCN
------------------- ----------
2017-09-23 02:12:55    989929
2017-09-23 02:17:44    990322
2017-09-23 02:23:02    990432
2017-09-23 02:27:44    990533

删除SMON_SCN_TIME表
此时查询表已经不存在

SQL> drop table smon_scn_time;
Table dropped.
SQL> select time_dp,scn from smon_scn_time where rownum<5;
select time_dp,scn from smon_scn_time where rownum<5;
                                      *
ERROR at line 1:
ORA-00942: table or view does not exist

查询SMON_SCN_TIME表创建语句（这里使用的是11g 11.2.04的环境）
SMON_SCN_TIME表重建语句在 $ORACLE_HOME/rdbms/admin/dtxnspc.bsq

rem
rem create the scn<->time tracking table that smon will maintain
rem as a circular queue - notice that we populate the entire
rem table with at least 144000 entries (enough for 5 days).
rem
rem -"thread" is for backward compatibility and is always 0
rem -"orig_thread" is for upgrade/downgrade
rem - scn_wrp, scn_bas, and time_dp are for backward compatibility
rem   and not queried by the ktf layer.
rem Also create the props$ entry to indicate that the mapping is in GMT.
rem
Rem Add to props$ the flashback timestamp time zone information.
Rem Both flashback timestamp and the timestamp in smon_scn_time table are
Rem now recorded in GMT.
insert into props$ (name, value$, comment$)
  values('Flashback Timestamp TimeZone', 'GMT',
         'Flashback timestamp created in GMT');
commit;
/
create cluster smon_scn_to_time_aux (
  thread number                         /* thread, compatibility */
) tablespace SYSAUX
/
create index smon_scn_to_time_aux_idx on cluster smon_scn_to_time_aux
/
-----
create table smon_scn_time (
  thread number,                         /* thread, compatibility */
  time_mp number,                        /* time this recent scn represents */
  time_dp date,                          /* time as date, compatibility */
  scn_wrp number,                        /* scn.wrp, compatibility */
  scn_bas number,                        /* scn.bas, compatibility */
  num_mappings number,
  tim_scn_map raw(1200),
  scn number default 0,                  /* scn */
  orig_thread number default 0           /* for downgrade */
) cluster smon_scn_to_time_aux (thread)
/
create unique index smon_scn_time_tim_idx on smon_scn_time(time_mp)
  tablespace SYSAUX
/
create unique index smon_scn_time_scn_idx on smon_scn_time(scn)
  tablespace SYSAUX
/

执行创建语句

create table smon_scn_time (
  thread number,                         /* thread, compatibility */
  time_mp number,                        /* time this recent scn represents */
  time_dp date,                          /* time as date, compatibility */
  scn_wrp number,                        /* scn.wrp, compatibility */
  scn_bas number,                        /* scn.bas, compatibility */
  num_mappings number,
  tim_scn_map raw(1200),
  scn number default 0,                  /* scn */
  orig_thread number default 0           /* for downgrade */
) cluster smon_scn_to_time_aux (thread)
/
create unique index smon_scn_time_tim_idx on smon_scn_time(time_mp)
  tablespace SYSAUX
/
create unique index smon_scn_time_scn_idx on smon_scn_time(scn)
  tablespace SYSAUX
/

查询SMON_SCN_TIME状态

SQL> analyze table SMON_SCN_TIME validate structure cascade online;
Table analyzed.

SQL> select time_dp,scn from smon_scn_time where rownum<5;
TIME_DP            SCN
------------------- ----------
2017-10-11 02:30:15    1125028      #(这里的时间和上面不一致是因为我的是虚拟机之前做实验恢复过，导致时间不连续)
2017-10-11 02:35:30    1125305

二、创建SMON_SCN_TIME表索引

确认表上smon_scn_time是否有损坏

SQL> analyze table SMON_SCN_TIME validate structure;
Table analyzed.

查询表上索引

SQL> set lines 120
SQL> col index_name for a40
SQL> col index_type for a20
SQL> col owner for a20   
SQL> select index_name,index_type,owner from dba_indexes where table_name='SMON_SCN_TIME';
INDEX_NAME                 INDEX_TYPE          OWNER
---------------------------------------- -------------------- --------------------
SMON_SCN_TIME_SCN_IDX             NORMAL           SYS
SMON_SCN_TIME_TIM_IDX             NORMAL           SYS

获取索引的DDL语句

SQL> select dbms_metadata.get_ddl('INDEX','SMON_SCN_TIME_TIM_IDX','SYS') FROM DUAL;
DBMS_METADATA.GET_DDL('INDEX','SMON_SCN_TIME_TIM_IDX','SYS')
--------------------------------------------------------------------------------
  CREATE UNIQUE INDEX "SYS"."SMON_SCN_TIME_TIM_IDX" ON "SYS"."SMON_SCN_TIME" ("TIME_MP")
  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "SYSAUX"
SQL> SELECT DBMS_METADATA.GET_DDL('INDEX','SMON_SCN_TIME_SCN_IDX','SYS') FROM DUAL;
DBMS_METADATA.GET_DDL('INDEX','SMON_SCN_TIME_SCN_IDX','SYS')
--------------------------------------------------------------------------------
  CREATE UNIQUE INDEX "SYS"."SMON_SCN_TIME_SCN_IDX" ON "SYS"."SMON_SCN_TIME" ("SCN")
  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "SYSAUX"

删除索引

SQL> drop index sys.smon_scn_time_tim_idx;
Index dropped.
SQL> drop index sys.smon_scn_time_scn_idx;
Index dropped.

验证SMON_SCN_TIME表的有效性

SQL> analyze table smon_scn_time validate structure cascade online;
Table analyzed.

创建索引

SQL>   CREATE UNIQUE INDEX "SYS"."SMON_SCN_TIME_TIM_IDX" ON "SYS"."SMON_SCN_TIME" ("TIME_M
P")  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "SYSAUX" ;

Index created.

SQL>   CREATE UNIQUE INDEX "SYS"."SMON_SCN_TIME_SCN_IDX" ON "SYS"."SMON_SCN_TIME" ("SCN")
  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "SYSAUX" ;

Index created.

验证SMON_SCN_TIME表状态

SQL> analyze table smon_scn_time validate structure cascade online;
Table analyzed.

创建完成

三、设置12500事件停止SMON进程对SMON_SCN_TIME的写入和关闭12500事件

正常SMON_TIME_SCN的记录

SQL> select sysdate from dual;
SYSDATE
-------------------
2017-10-11 11:05:02
SQL> select count(1) from smon_scn_time;
  COUNT(1)
----------
     4
SQL> ^Cse  
SQL> select count(1) from smon_scn_time;
  COUNT(1)
----------
     8
SQL> select sysdate from dual;
SYSDATE
-------------------
2017-10-11 11:14:01

设置12500事件后

SQL> alter system set events '12500 trace name context forever,level 10';
System altered.
SQL> select count(1) from smon_scn_time;
  COUNT(1)
----------
     8
SQL> select sysdate from dual;
SYSDATE
-------------------
2017-10-11 11:15:49
SQL> select count(1) from smon_scn_time;
  COUNT(1)
----------
     8
SQL> select sysdate from dual;
SYSDATE
-------------------
2017-10-11 11:28:37

关闭12500事件

SQL> alter system set events '12500 trace name context off';
System altered.