[oracle@zhongwc1 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Wed Jan 23 17:02:01 2013 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 6
[oracle@zhongwc1 ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jan 23 17:02:01 2013
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
SQL> set lines 200
SQL> select instance_name,host_name from v$instance;
INSTANCE_NAME HOST_NAME
---------------- ----------------------------------------------------------------
zhongwc1 zhongwc1.oracle.com
SQL> select instance_name,host_name from gv$instance;
INSTANCE_NAME HOST_NAME
---------------- ----------------------------------------------------------------
zhongwc1 zhongwc1.oracle.com
zhongwc2 zhongwc2.oracle.com
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
NO
SQL> show release
release 1102000300
SQL> alter database flashback on;
Database altered.
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
YES
SQL> conn zwc
Enter password:
Connected.
SQL> create table t_zhongwc as select * from dba_objects;
Table created.
SQL> select count(*) from t_zhongwc;
COUNT(*)
----------
75289
SQL>
记录当前的scn(oracle11gR2可以在open状态flashback on)
SQL> select current_scn from v$database;
CURRENT_SCN
-----------
1395475
截断t_zhongwc表
SQL> truncate table t_zhongwc;
Table truncated.
SQL> select count(*) from t_zhongwc;
COUNT(*)
----------
0
开始执行闪回,关闭所有实例,启动zhongwc1到mount,闪回到scn 1395475,以只读模式打开验证
[oracle@zhongwc1 ~]$ srvctl stop database -d zhongwc
[oracle@zhongwc1 ~]$ su - grid -c "crsctl stat res -t"
Password:
--------------------------------------------------------------------------------
NAME TARGET STATE SERVER STATE_DETAILS
--------------------------------------------------------------------------------
Local Resources
--------------------------------------------------------------------------------
ora.CRS.dg
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
ora.DATADG.dg
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
ora.FRADG.dg
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
ora.LISTENER.lsnr
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
ora.asm
ONLINE ONLINE zhongwc1 Started
ONLINE ONLINE zhongwc2 Started
ora.gsd
OFFLINE OFFLINE zhongwc1
OFFLINE OFFLINE zhongwc2
ora.net1.network
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
ora.ons
ONLINE ONLINE zhongwc1
ONLINE ONLINE zhongwc2
--------------------------------------------------------------------------------
Cluster Resources
--------------------------------------------------------------------------------
ora.LISTENER_SCAN1.lsnr
1 ONLINE ONLINE zhongwc1
ora.cvu
1 ONLINE ONLINE zhongwc1
ora.oc4j
1 ONLINE ONLINE zhongwc1
ora.scan1.vip
1 ONLINE ONLINE zhongwc1
ora.zhongwc.db
1 OFFLINE OFFLINE Instance Shutdown
2 OFFLINE OFFLINE Instance Shutdown
ora.zhongwc1.vip
1 ONLINE ONLINE zhongwc1
ora.zhongwc2.vip
1 ONLINE ONLINE zhongwc2
[oracle@zhongwc1 ~]$
[oracle@zhongwc1 ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jan 23 17:22:40 2013
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup mount
ORACLE instance started.
Total System Global Area 1269366784 bytes
Fixed Size 2227984 bytes
Variable Size 889192688 bytes
Database Buffers 369098752 bytes
Redo Buffers 8847360 bytes
Database mounted.
SQL> flashback database to scn 1395475;
Flashback complete.
SQL> alter database open read only;
Database altered.
SQL> conn zwc
Enter password:
Connected.
SQL> select count(*) from t_zhongwc;
COUNT(*)
----------
75289
resetlogs打开数据库,启动zhongwc2
SQL> shutdown immediate
ORA-01031: insufficient privileges
SQL> conn / as sysdba
Connected.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 1269366784 bytes
Fixed Size 2227984 bytes
Variable Size 889192688 bytes
Database Buffers 369098752 bytes
Redo Buffers 8847360 bytes
Database mounted.
SQL> alter database open resetlogs;
Database altered.
SQL> !srvctl start instance -d zhongwc -i zhongwc2
SQL> col host_name format a20
SQL> set lines 300
SQL> select INSTANCE_NAME,HOST_NAME,VERSION,STARTUP_TIME,STATUS,ACTIVE_STATE,INSTANCE_ROLE,DATABASE_STATUS from gv$INSTANCE;
INSTANCE_NAME HOST_NAME VERSION STARTUP_TIME STATUS ACTIVE_ST INSTANCE_ROLE DATABASE_STATUS
---------------- -------------------- ----------------- ----------------------- ------------ --------- ------------------ -----------------
zhongwc1 zhongwc1.oracle.com 11.2.0.3.0 23-JAN-2013 17:30:37 OPEN NORMAL PRIMARY_INSTANCE ACTIVE
zhongwc2 zhongwc2.oracle.com 11.2.0.3.0 23-JAN-2013 17:34:30 OPEN NORMAL PRIMARY_INSTANCE ACTIVE
也可以基于时间戳进行闪回数据库
SQL> select to_char(scn_to_timestamp(1395475),'yyyy-mm-dd hh24:mi:ss') time_stamp from dual;
TIME_STAMP
-------------------
2013-01-23 17:14:05
SQL> flashback database to timestamp to_timestamp('2013-01-23 17:14:05','yyyy-mm-dd hh24:mi:ss');
flashback database to timestamp to_timestamp('2013-01-23 17:14:05','yyyy-mm-dd hh24:mi:ss')
*
ERROR at line 1:
ORA-38757: Database must be mounted and not open to FLASHBACK.
,
掌握添加MySQL用户的方法对于数据库管理员和开发者至关重要,因为它确保数据库的安全性和访问控制。1)使用CREATEUSER命令创建新用户,2)通过GRANT命令分配权限,3)使用FLUSHPRIVILEGES确保权限生效,4)定期审计和清理用户账户以维护性能和安全。

chosecharforfixed-lengthdata,varcharforvariable-lengthdata,andtextforlargetextfield.1)chariseffity forconsistent-lengthdatalikecodes.2)varcharsuitsvariable-lengthdatalikenames,ballancingflexibilitibility andperformance.3)

在MySQL中处理字符串数据类型和索引的最佳实践包括:1)选择合适的字符串类型,如CHAR用于固定长度,VARCHAR用于可变长度,TEXT用于大文本;2)谨慎索引,避免过度索引,针对常用查询创建索引;3)使用前缀索引和全文索引优化长字符串搜索;4)定期监控和优化索引,保持索引小巧高效。通过这些方法,可以在读取和写入性能之间取得平衡,提升数据库效率。

ToaddauserremotelytoMySQL,followthesesteps:1)ConnecttoMySQLasroot,2)Createanewuserwithremoteaccess,3)Grantnecessaryprivileges,and4)Flushprivileges.BecautiousofsecurityrisksbylimitingprivilegesandaccesstospecificIPs,ensuringstrongpasswords,andmonitori

tostorestringsefliceflicyInmySql,ChooSetherightDataTypeBasedyOrneOrneEds:1)USEcharforFixed-LengthStstringStringStringSlikeCountryCodes.2)UseVarcharforvariable-lengtthslikenames.3)USETEXTCONTENT.3)

选择MySQL的BLOB和TEXT数据类型时,BLOB适合存储二进制数据,TEXT适合存储文本数据。1)BLOB适用于图片、音频等二进制数据,2)TEXT适用于文章、评论等文本数据,选择时需考虑数据性质和性能优化。

No,youshouldnotusetherootuserinMySQLforyourproduct.Instead,createspecificuserswithlimitedprivilegestoenhancesecurityandperformance:1)Createanewuserwithastrongpassword,2)Grantonlynecessarypermissionstothisuser,3)Regularlyreviewandupdateuserpermissions

mySqlStringDatatatPessHouldBechoseBeadeDataCharacteristicsAndUsecases:1)USECHARFORFIXED LENGTHSTRINGSTRINGSLIKECOUNTRYCODES.2)USEDES.2)usevarcharforvariable-lengtthstringstringstringstringstringstringstringslikenames.3)usebinaryorvarrinaryorvarinarydatalbonydatalgebgeenfopical.4)


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