分类目录归档：Data Guard

11G RAC TO 11G RAC ADG SWITCHOVER

发表于 2013 年 6 月 25 日由惜分飞

11G RAC TO 11G RAC ADG切换过程
主库准备工作

SQL> select inst_id,database_role,OPEN_MODE from  gv$database;

   INST_ID DATABASE_ROLE    OPEN_MODE
---------- ---------------- --------------------
         2 PRIMARY          READ WRITE
         1 PRIMARY          READ WRITE

[oracle@q9db02 ~]$ srvctl stop instance -d q9db -i q9db2

SQL> select inst_id,database_role,OPEN_MODE from  gv$database;

   INST_ID DATABASE_ROLE    OPEN_MODE
---------- ---------------- --------------------
         1 PRIMARY          READ WRITE

SQL> CREATE RESTORE POINT SWITCHOVER_START_GRP GUARANTEE FLASHBACK DATABASE;

Restore point created.

备库准备工作

SQL> select inst_id,database_role,OPEN_MODE from  gv$database;

   INST_ID DATABASE_ROLE    OPEN_MODE
---------- ---------------- --------------------
         2 PHYSICAL STANDBY READ ONLY WITH APPLY
         1 PHYSICAL STANDBY READ ONLY WITH APPL

[oracle@q9adg02 ~]$ srvctl stop instance -d q9db_adg -i q9db2

SQL> select inst_id,database_role,OPEN_MODE from  gv$database;

   INST_ID DATABASE_ROLE    OPEN_MODE
---------- ---------------- --------------------
         1 PHYSICAL STANDBY READ ONLY WITH APPL


SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Database altered.

SQL> CREATE RESTORE POINT SWITCHOVER_START_GRP GUARANTEE FLASHBACK DATABASE;

Restore point created.

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;

Database altered.

主库切换日志,观察备库

--主库
SQL> alter system switch logfile;

System altered.

SQL> /

System altered.

--备库
[oracle@q9adg01 trace]$ tail -f alert_q9db1.log 
Tue Jun 25 15:35:27 2013
RFS[10]: Selected log 52 for thread 1 sequence 4777 dbid 844605368 branch 817913807
Tue Jun 25 15:35:28 2013
Archived Log entry 4889 added for thread 1 sequence 4776 ID 0x3545ffea dest 1:
Tue Jun 25 15:35:28 2013
Media Recovery Waiting for thread 1 sequence 4777 (in transit)
Tue Jun 25 15:35:28 2013
RFS[11]: Selected log 72 for thread 2 sequence 1630 dbid 844605368 branch 817913807
Recovery of Online Redo Log: Thread 1 Group 52 Seq 4777 Reading mem 0
  Mem# 0: +DATA/q9db_adg/onlinelog/group_52.1564.818724635
Media Recovery Waiting for thread 2 sequence 1630 (in transit)
Recovery of Online Redo Log: Thread 2 Group 72 Seq 1630 Reading mem 0
  Mem# 0: +DATA/q9db_adg/onlinelog/group_72.1575.818724653
Tue Jun 25 15:35:30 2013
Archived Log entry 4890 added for thread 2 sequence 1629 ID 0x3545ffea dest 1:

几乎同步进行表示主备日志传输应用正常

主库切换

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS
--------------------
TO STANDBY

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY WITH SESSION SHUTDOWN;


Database altered.

备库切换

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS
--------------------
TO PRIMARY

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;

Database altered.

SQL> ALTER DATABASE OPEN;

Database altered.

继续处理主库

SQL> shutdown immediate
ORA-01092: ORACLE instance terminated. Disconnection forced
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, Data Mining
and Real Application Testing options
[oracle@q9db01 ogg]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Tue Jun 25 14:13:58 2013

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup mount
ORACLE instance started.

Total System Global Area 1.6034E+11 bytes
Fixed Size                  2236968 bytes
Variable Size            2.5770E+10 bytes
Database Buffers         1.3422E+11 bytes
Redo Buffers              352468992 bytes
Database mounted.
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;


Database altered.

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE cancel;

Database altered.

SQL> alter database open;

Database altered.

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;


Database altered.

清理快照

--主库
SQL> DROP RESTORE POINT SWITCHOVER_START_GRP;

Restore point dropped.

--备库
SQL> startup mount
ORACLE instance started.

Total System Global Area 1.6034E+11 bytes
Fixed Size                  2236968 bytes
Variable Size            2.7380E+10 bytes
Database Buffers         1.3261E+11 bytes
Redo Buffers              352468992 bytes
Database mounted.
SQL> DROP RESTORE POINT SWITCHOVER_START_GRP;

Restore point dropped.

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;


Database altered.

SQL>  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;


Database altered.

SQL> alter database open;

Database altered.

SQL>  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;

Database altered.

启动主备另外节点

--主库
[oracle@q9db01 ~]$ srvctl start instance -d q9db -i q9db2
--备库
[oracle@q9adg02 ~]$ srvctl start instance -d q9db_adg -i q9db2

补充说明:如果出现日志切换暂时不能传输

备库执行(因为重启动态监听没有马上别识别)
alter system register;
主库执行
alter system set log_archive_dest_state_2=enable;

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修改dataguard主库redo组数和大小

发表于 2013 年 5 月 14 日由惜分飞

在一个dg环境中，配置的是实时同步,需要增加主库的redo大小和组数,本来是一个很简单的问题,解决思路是：先备库增加standby redo删除老standby redo,然后主库增加redo删除老redo,备库增加新redo删除老redo,最后主库增加standby redo。但是在实施过程中，遇到了一些细节性的问题，主要是学习到了log_file_name_convert如果不配置,将导致备库redo 文件不能被删除

standby redo log管理
增加standby redo log

SQL> alter database add standby logfile group 8 ('/data/oradata/wasudb/st_redo08.log') size 200M; 
alter database add standby logfile group 8 ('/data/oradata/wasudb/st_redo08.log') size 200M
*
ERROR at line 1:
ORA-01156: recovery in progress may need access to files

SQL> alter database recover managed standby database cancel;

Database altered.

SQL> alter database add standby logfile group 9 ('/data/oradata/wasudb/st_redo09.log') size 200M; 

Database altered.

SQL> alter database add standby logfile group 10 ('/data/oradata/wasudb/st_redo10.log') size 200M; 

Database altered.

SQL> alter database add standby logfile group 11 ('/data/oradata/wasudb/st_redo11.log') size 200M; 

Database altered.

SQL> alter database add standby logfile group 12 ('/data/oradata/wasudb/st_redo12.log') size 200M; 

Database altered.

删除standby redo log

SQL> alter database drop logfile group 4;
alter database drop logfile group 4
*
ERROR at line 1:
ORA-00261: log 4 of thread 1 is being archived or modified
ORA-00312: online log 4 thread 1: '/data/oradata/wasudb/st_redo04.log'


SQL> alter database drop logfile group 5;;

Database altered.

SQL> alter database drop logfile group 6;

Database altered.

SQL> alter database drop logfile group 7;

Database altered.

--在主库多次执行switch logfile

SQL>  alter database drop logfile group 4;

Database altered.

主库redo log 管理
增加redo log

SQL> alter database add logfile group 21 ('/data/oradata/wasudb/redo21.log') size 200m;

Database altered.

SQL> alter database add logfile group 22 ('/data/oradata/wasudb/redo22.log') size 200m; 

Database altered.

SQL> alter database add logfile group 23 ('/data/oradata/wasudb/redo23.log') size 200m; 

Database altered.

SQL> alter database add logfile group 24 ('/data/oradata/wasudb/redo24.log') size 200m;

Database altered.

删除redo log

SQL> alter database drop logfile group 1;

Database altered.

SQL> alter database drop logfile group 2;

Database altered.

SQL> alter database drop logfile group 3;

Database altered.
--这里涉及到多次switch logfile,需要确定redo是inactive才能够删除

备库redo log管理
增加redo log

SQL> alter database add logfile group 21 ('/data/oradata/wasudb/redo21.log') size 200m; 
alter database add logfile group 21 ('/data/oradata/wasudb/redo21.log') size 200m
*
ERROR at line 1:
ORA-01275: Operation ADD LOGFILE is not allowed if standby file management is automatic.


SQL>  alter system set standby_file_management=manual;

System altered.

SQL> alter database add logfile group 21 ('/data/oradata/wasudb/redo21.log') size 200m;

Database altered.

SQL> alter database add logfile group 22 ('/data/oradata/wasudb/redo22.log') size 200m; 

Database altered.

SQL> alter database add logfile group 23 ('/data/oradata/wasudb/redo23.log') size 200m; 

Database altered.

SQL> alter database add logfile group 24 ('/data/oradata/wasudb/redo24.log') size 200m;

Database altered.

删除redo log

SQL> alter database drop logfile group 1;
alter database drop logfile group 1
*
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of instance wasudb (thread 1)
ORA-00312: online log 1 thread 1: '/data/oradata/wasudb/redo01.log'

SQL>  ALTER DATABASE CLEAR LOGFILE GROUP 1;
 ALTER DATABASE CLEAR LOGFILE GROUP 1
*
ERROR at line 1:
ORA-19527: physical standby redo log must be renamed
ORA-00312: online log 1 thread 1: '/data/oradata/wasudb/redo01.log'

SQL> show parameter NAME_CONVERT

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_file_name_convert                 string
log_file_name_convert                string

SQL> alter system set log_file_name_convert='/data/oradata/wasudb','/data/oradata/wasudb' scope=spfile;

System altered.

SQL>  alter system set db_file_name_convert='/data/oradata/wasudb','/data/oradata/wasudb' scope=spfile;

System altered.

--重启数据库

SQL> show parameter file_name_convert;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_file_name_convert                 string      /data/oradata/wasudb, /data/or
                                                 adata/wasudb
log_file_name_convert                string      /data/oradata/wasudb, /data/or
                                                 adata/wasudb

SQL> alter database drop logfile group 1;
alter database drop logfile group 1
*
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of instance wasudb (thread 1)
ORA-00312: online log 1 thread 1: '/data/oradata/wasudb/redo01.log'

SQL> ALTER DATABASE CLEAR LOGFILE GROUP 1;

Database altered.

SQL> alter database drop logfile group 1;

Database altered.

SQL> ALTER DATABASE CLEAR LOGFILE GROUP 2;

Database altered.

SQL> alter database drop logfile group 2;

Database altered.

SQL> ALTER DATABASE CLEAR LOGFILE GROUP 3;

Database altered.

SQL> alter database drop logfile group 3;

Database altered.

主库standby redo log管理
增加standby redo

SQL> alter database add logfile group 21 ('/data/oradata/wasudb/redo21.log') size 200m;

Database altered.

SQL> alter database add logfile group 22 ('/data/oradata/wasudb/redo22.log') size 200m; 

Database altered.

SQL> alter database add logfile group 23 ('/data/oradata/wasudb/redo23.log') size 200m; 

Database altered.

SQL> alter database add logfile group 24 ('/data/oradata/wasudb/redo24.log') size 200m;

Database altered.

删除standby redo

SQL> alter database drop logfile group 4;

Database altered.

SQL> alter database drop logfile group 5;

Database altered.

SQL> alter database drop logfile group 6;

Database altered.

SQL> alter database drop logfile group 7;

Database altered.

后续工作

SQL> alter system set standby_file_management=auto;

System altered.

SQL> alter database recover managed standby database using current logfile disconnect from session;

Database altered.

至此修改dataguard环境中的redo大小和增加redo组数的操作基本完成.在这里主要修正了自己以前对log_file_name_convert的认识，我以前以为如果我的主备库redo对应的目录一致不用配置该参数,今天通过查询MOS发现从10.2开始数据库为了能实现dg的快速切换在mrp启动的时候会去尝试清理备库redo,如果备库没有redo,或者log_file_name_convert配置不正确导致不能正常执行这个清理工作,数据库就会报ORA-19527,特别是在mrp进程启动之时.对于本次出现执行CLEAR LOGFILE命令也出现该问题,确实有点过犹不及了.这里也就是提醒我们:就算redo file,datafile主备位置相同,也建议配置log_file_name_convert和db_file_name_convert参数,提高dg健壮性.

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EXADATA与非EXADATA搭建DATAGURAD关于EHCC特性测试

发表于 2012 年 12 月 12 日由惜分飞

随着xd的越来越普及，不少的企业使用了xd，但是不少企业因为资金有限，只有一台xd，但是为了实现数据的容灾，可能会使用一台非xd的机器来通过dataguard来实现容灾,但是因为xd的ehcc新特性,官方宣传是只在xd中支持,如果dg的备库不是xd。那么会怎么样,这里通过测试得出如下一些结论：xd与非xd可以构造dg,ehcc功能在xd上无法高效使用。对于这样的环境条件下,使用ORACLE自带压缩效率更高.针对ehcc压缩效率很低,个人猜测,是因为xd检查到备库是非xd环境,直接对ehcc进行了降级压缩处理,从而出现了ehcc的压缩效率比oltp还低(牺牲了xd的性能,确保了数据的安全,看来xd的设计还是考虑的比较全面)
xd基本信息

SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

SQL> show parameter clu;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
cluster_database                     boolean     TRUE
cluster_database_instances           integer     2
cluster_interconnects                string

SQL> SELECT OPEN_MODE, DATABASE_ROLE ,NAME FROM V$DATABASE;

OPEN_MODE            DATABASE_ROLE    NAME
-------------------- ---------------- ---------
READ WRITE           PRIMARY          xxxxxx

SQL> !uname -a
Linux dm01db02 2.6.18-194.3.1.0.4.el5 #1 SMP Sat Feb 19 03:38:37 EST 2011 x86_64 x86_64 x86_64 GNU/Linux

xd创建模拟表

SQL> create table t_FF_c compress as select  * from dba_objects;

Table created.

SQL> create table t_FF_c_o compress for oltp  as select  * from dba_objects;

Table created.

SQL> create table t_FF_q_l compress for query low as select  * from dba_objects;

Table created.

SQL> create table t_FF_q_h compress for query high  as select  * from dba_objects;

Table created.

SQL> create table t_FF_a_l compress for archive low  as select  * from dba_objects;

Table created.

SQL> create table t_FF_a_h compress for archive high as select * from dba_objects;

Table created.

SQL> create table t_ff as select * from dba_objects;

Table created.

xd查询模拟表

SQL> select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%';  2    3  

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   11
SYS                            T_FF_A_H                               10 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC

通过这里发现,带有非dg的xd使用ehcc压缩效率都低了很多

非xd备库基本信息

SQL> SELECT OPEN_MODE, DATABASE_ROLE ,NAME FROM V$DATABASE;

OPEN_MODE            DATABASE_ROLE    NAME
-------------------- ---------------- ---------
READ ONLY WITH APPLY PHYSICAL STANDBY xxxxxx

SQL> show parameter clu;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
cluster_database                     boolean     FALSE
cluster_database_instances           integer     1
cluster_interconnects                string

SQL> !uname -a
Linux oradg 2.6.18-238.el5xen #1 SMP Sun Dec 19 14:42:02 EST 2010 x86_64 x86_64 x86_64 GNU/Linux

查询非xd dg备库

SQL> select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%'; 

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   11
SYS                            T_FF_A_H                               10 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC

SQL> SELECT COUNT(*) FROM T_FF_Q_L;

  COUNT(*)
----------
     94709

SQL> SELECT COUNT(*) FROM T_FF_Q_H;

  COUNT(*)
----------
     94710

SQL> SELECT COUNT(*) FROM T_FF_C_O;

  COUNT(*)
----------
     94708

SQL> SELECT COUNT(*) FROM T_FF_C;

  COUNT(*)
----------
     94707

SQL> SELECT COUNT(*) FROM T_FF_A_L;

  COUNT(*)
----------
     94711

SQL> SELECT COUNT(*) FROM T_FF_A_H;

  COUNT(*)
----------
     94712

SQL> select count(*) from t_FF;

  COUNT(*)
----------
    94713

通过这里测试证明,对于非xd dg库,可以正常的查询xd上的ehcc相关表,而且相关大小也相同(物理dg当然相同了)

测试xd与非xd dg测试ehcc的dml操作

--xd 主库
SQL> update t_ff_a_h set owner='www.xifenfei.com';

94712 rows updated.

SQL> commit;

Commit complete.

SQL>  select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%';  2    3  

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   11
SYS                            T_FF_A_H                               11 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC

7 rows selected.

SQL> alter system switch logfile;

System altered.

--非xd 备库
SQL> select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%';  

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   11
SYS                            T_FF_A_H                               11 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC

证明对于xd与非xd构成的dg环境,可以执行dml操作.

测试xd与非xd dg的ehcc的append操作

--xd准备三张测试空表
SQL> create table t_FF_a_l_1 compress for archive low as select * from t_FF  where 1=0;

Table created.

SQL> create table t_FF_a_h_1 compress for archive high  as select * from t_FF  where 1=0;

Table created.

SQL>truncate table t_FF;

Table truncated.

--插入数据(每个表执行5次)
SQL> insert /*+ APPEND */ into t_FF_a_l_1 select * from dba_objects; 

94714 rows created.

SQL> commit;

Commit complete.


SQL> insert /*+ APPEND */ into t_FF_h_l_1 select * from dba_objects; 

94714 rows created.

SQL> commit;

Commit complete.

SQL> insert /*+ APPEND */ into t_FF select * from dba_objects; 

94714 rows created.

SQL> commit;

Commit complete.

--查看相关表数据量
SQL> select count(*) from t_FF_a_l_1;

  COUNT(*)
----------
    473570

SQL> select count(*) from t_FF_a_h_1;

  COUNT(*)
----------
    473570

SQL> select count(*) from t_FF;
  COUNT(*)
----------
    473570

--查看xd主库
SQL> select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%'; 

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   52
SYS                            T_FF_A_H                               11 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC
SYS                            T_FF_A_H_1                             47 ARCHIVE HIGH
SYS                            T_FF_A_L_1                             47 ARCHIVE LOW

--查看非xd备库
SQL> select s.owner,segment_name,s.bytes/1024/1024 t_size,compress_for 
from dba_segments s,dba_tables t
where s.owner=t.owner and t.table_name=s.segment_name  and t.table_name like 'T_FF%'; 

OWNER                          SEGMENT_NAME                       T_SIZE COMPRESS_FOR
------------------------------ ------------------------------ ---------- ------------
SYS                            T_FF                                   52
SYS                            T_FF_A_H                               11 ARCHIVE HIGH
SYS                            T_FF_A_L                               10 ARCHIVE LOW
SYS                            T_FF_Q_H                               10 QUERY HIGH
SYS                            T_FF_Q_L                               10 QUERY LOW
SYS                            T_FF_C_O                                4 OLTP
SYS                            T_FF_C                                  4 BASIC
SYS                            T_FF_A_H_1                             47 ARCHIVE HIGH
SYS                            T_FF_A_L_1                             47 ARCHIVE LOW

试验整体结论
1.xd可以与非xd机器构建dg容灾环境(不会因为非dg不支持ehcc而导致无法搭建他们之间的dg)
2.xd与非xd的dg,ehcc功能大大缩水,基本上和非压缩状态差不多,比OLTP低很多
3.xd与非xd的dg在备库中支持select,dml,hint append等操作,这些操作是因为ehcc表在xd端就进行了ehcc降级导致

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分类目录归档：Data Guard

11G RAC TO 11G RAC ADG SWITCHOVER

修改dataguard主库redo组数和大小

EXADATA与非EXADATA搭建DATAGURAD关于EHCC特性测试

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分类目录归档：Data Guard

11G RAC TO 11G RAC ADG SWITCHOVER

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