分类目录归档：Oracle

模拟ORA-04043并解决

发表于 2012 年 3 月 29 日由惜分飞

创建两张模拟表

SQL> select * from v$version;

BANNER
------------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
PL/SQL Release 9.2.0.4.0 - Production
CORE    9.2.0.3.0       Production
TNS for Linux: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production


SQL> create table sys_xifenfei as           
  2  select * from dba_tables;

Table created.

SQL> create table chf.chf_xifenfei as
  2  select * from dba_tables;

Table created.

启动数据库到mount状态查询表

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area  353441008 bytes
Fixed Size                   451824 bytes
Variable Size             184549376 bytes
Database Buffers          167772160 bytes
Redo Buffers                 667648 bytes
Database mounted.
SQL> desc dba_tables;
ERROR:
ORA-04043: object dba_tables does not exist


SQL> desc sys_xifenfei
ERROR:
ORA-04043: object sys_xifenfei does not exist


SQL> desc chf.chf_xifenfei
ERROR:
ORA-04043: object chf.chf_xifenfei does not exist

打开数据库查询

SQL> alter database open;

Database altered.


SQL> select count(*) from sys_xifenfei;
select count(*) from sys_xifenfei
                     *
ERROR at line 1:
ORA-00942: table or view does not exist


SQL> select count(*) from chf.chf_xifenfei;

  COUNT(*)
----------
       868

SQL> select count(*) from dba_tables;
select count(*) from dba_tables
                     *
ERROR at line 1:
ORA-00942: table or view does not exist

解决问题

SQL> alter system flush shared_pool;

System altered.


SQL> select count(*) from dba_tables;

  COUNT(*)
----------
       869

SQL> select count(*) from sys_xifenfei;

  COUNT(*)
----------
       867

MOS解释
ORA-4043 On DBA_* Views If They Are Described In Mount Stage [ID 296235.1]

Available workarounds are:
1) Don't describe the dba_* views at mount stage.
OR
2) If you issue DESC of any DBA_*views at mount stage,
    then shutdown and restart the DB instance.
OR
3) Flush the shared pool.
SQL> Alter system flush shared_pool;
and then reissue the failing command.

在10g中open库后提示也为类此ORA-04043: object dba_tables does not exist

发表在 ORA-xxxxx | 标签为 ORA-04043 | 评论关闭

关于9I中sga_max_size参数描述

发表于 2012 年 3 月 29 日由惜分飞

不设置sga_max_size参数

SQL> show sga;

Total System Global Area  420549952 bytes
Fixed Size                   451904 bytes
Variable Size             201326592 bytes
Database Buffers          218103808 bytes
Redo Buffers                 667648 bytes

SQL> select sum(bytes)from v$sgastat;

SUM(BYTES)
----------
 420538688

SQL> !ipcs -m       

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x9ba476a4 65536      oracle    640        440401920  65       

SQL> alter system set db_cache_size=300M;
alter system set db_cache_size=300M
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00384: Insufficient memory to grow cache

1)当sga_max_size不设置时，数据库启动时，会使用数据库默认分配sga大小为初始化值
2)当sga_max_size不设置时，不能在线扩展组件内存大小(使得sga大于当前大小)

设置sga_max_size参数

SQL>  alter system set sga_max_size=600M scope=spfile;

System altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup 
ORACLE instance started.

Total System Global Area  638654020 bytes
Fixed Size                   452164 bytes
Variable Size             419430400 bytes
Database Buffers          218103808 bytes
Redo Buffers                 667648 bytes
Database mounted.
Database opened.
SQL> !ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x9ba476a4 98304      oracle    640        658505728  65                      

SQL> select sum(bytes)from v$sgastat;

SUM(BYTES)
----------
 420538948

SQL> alter system set db_cache_size=405M;

System altered.


SQL> select 638654020/1024/1024 from dual;

638654020/1024/1024
-------------------
         609.067936

说明sga中剩余空闲内存0.01M
SQL> select 609.067936-sum(bytes)/1024/1024 from v$sgastat;

609.067936-SUM(BYTES)/1024/1024
-------------------------------
                     .010742244

继续增加组件大小
SQL> alter system set db_cache_size=416M;

System altered.

SQL> select sum(bytes)/1024/1024 from v$sgastat;

SUM(BYTES)/1024/1024
--------------------
          609.057194

SQL>  select 638654020/1024/1024 from dual;

638654020/1024/1024
-------------------
         609.067936

SQL> alter system set db_cache_size=417M;   
alter system set db_cache_size=417M
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00384: Insufficient memory to grow cache

这里显示，当db_cache_size增加到415M的时候，sga只有0.01M剩余
但是直到db_cache_size增加到417的时候才报错

1)当sga有剩余时，可以动态调整sga中的部分组件(java_pool_size不能在线设置)
2)当sga没有剩余时，如果继续增加某组件的内存，在一定的范围内，sga会自动调整其他组件大小，以实用该值增加

关于sga_max_size总结
1)如果你的系统内存比较紧张，对停机时间要求不是特别严格，那可以不设置sga_max_size参数，这样在重启数据库设置sga组件的时候，不会因忘记设置sga_max_size而导致不能正常启动
2)如果你的系统内存充足，对停机有严格限制，那建议设置一个较大的sga_max_size，后续可以根据需求动态在线调整sga部分组件

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关于SMON_SCN_TIME若干问题说明

发表于 2012 年 3 月 28 日由惜分飞

1.SMON_SCN_TIME表基础知识
0)作用
由smon收集scn和time映射关系，用于flashback/查询scn和time对应关系等操作

1)保留条数
官方文档给出说明instance number N * 12 times per hour * 24 hours * 5 days = 1440N rows，因为每次的时间间隔不是非常准确的5分钟，所以在具体的条数在实际生产环境中有一定的出入

2)采集和删除
smon进程没5分钟采集一次插入到SMON_SCN_TIME表中，同时将删除历史数据(超过5天前数据)，采用下面语句
delete from smon_scn_time where thread=0 and time_mp = (select min(time_mp) from smon_scn_time where thread=0)，如果有时候index出了问题，导致该语句执行很慢

3)当查询scn对应time，如果scn超过SMON_SCN_TIME表范围，将提示错误；或者查询time对应的scn，如果超过范围也同样报错。

2.当SMON_SCN_TIME表出现问题时，truncate操作语句

--找出CLUSTER
Select dbms_metadata.get_ddl('TABLE','SMON_SCN_TIME','SYS') FROM DUAL ;

9i
truncate CLUSTER "SYS"."SMON_SCN_TO_TIME";

10g
truncate  CLUSTER "SYS"."SMON_SCN_TO_TIME";

11g
truncate CLUSTER "SYS"."SMON_SCN_TO_TIME_AUX";

3.停止/开启smon进程收集scn信息

stop
alter system set events '12500 trace name context forever, level 10';

start
alter system set events '12500 trace name context off';

4.index异常处理

--找出index
Select index_name,index_type,owner from dba_indexes where table_name='SMON_SCN_TIME';
--对应index创建语句
Select dbms_metadata.get_ddl('INDEX','SMON_SCN_TIME_TIM_IDX','SYS') FROM DUAL;

--重建index
drop index smon_scn_time_scn_idx;
drop index smon_scn_time_tim_idx;
create unique index smon_scn_time_scn_idx on smon_scn_time(scn);
create unique index smon_scn_time_tim_idx on smon_scn_time(time_mp);
analyze table smon_scn_time validate structure cascade online;

--rebuild index
alter index sys.smon_scn_time_scn_idx rebuild online;
alter index sys.smon_scn_time_tim_idx rebuild online;
analyze table smon_scn_time validate structure cascade online;

补充知识点scn计算方法SCN=(SCN_WRP * 4294967296) + SCN_BAS

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分类目录归档：Oracle

模拟ORA-04043并解决

关于9I中sga_max_size参数描述

关于SMON_SCN_TIME若干问题说明

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分类目录归档：Oracle

模拟ORA-04043并解决

关于9I中sga_max_size参数描述

关于SMON_SCN_TIME若干问题说明

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