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12c Data Guard 日志传输模式-14
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2019-09-23
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AuthorYuchong.Xu Email:vc.123@qq.com 测试文档,若有问题请及时沟通
12c Data Guard 日志传输模式
1
far sync insntance:
特点是主库不必等待远程(异地)备库
apply redo
才确认事务提交
.
far sync instance
只能以
async
模式传出日志到
cascade database
A primary database can transport to a farsync in SYNC, FASTSYNC, or
ASYNC mode.
But, the farsync can transport to a standby database only in ASYNC mode.
The leg from the far sync to the terminal standby will always be async.
Though you should control the transport mode via redoroutes instead of
logxptmode.
When using the RedoRoutes parameter to con$gure redo transport, you have
the option of explicitly specify the transport mode to the speci$ed destination. If
you do not explicitly specify the transport mode as part of the RedoRoutes
parameter value, redo transport for that target defaults to the value speci$ed by
the target's LogXptMode parameter.
https://docs.oracle.com/database/121/SBYDB/create_fs.htm#GUID-
54F9001B-A5F2-4134-A6BA-521DC7E41E57
2
cascading standby
In particular, for a cascading standby (thus, for a DB in Standby Role), the
only valid attribute for the transport is ASYNC, meaning that synchronous
transport from a standby database to another is not possible. If ASYNC is
speci$ed then Real-Time cascade is used, if no transport attribute is speci$ed,
Real-Time cascade is disabled and the redo stream from the cascading to the
cascaded database is transported using the archived logs.
http://docs.oracle.com/database/121/SBYDB/log_transport.htm#SBYDB5122
https://docs.oracle.com/database/121/SBYDB/log_transport.htm#SBYDB5123
If you specify ASYNC transport mode on destinations 1 through 10, then
redo is shipped in real-time. If you do not specify a transport mode or you specify
SYNC on destinations 1 through 10, then redo is shipped in non-real-time.
Destinations 11 through 31 operate only in ASYNC (real-time) transport mode
11G :
• Redo Apply upon primary log switch.
• Cascading standby always lag behind $rst standby.
12c :
• First Standby can ship REDO in real time mode.
• No need to wait for primary database log switch.
this called real-time cascading standby.
so you can $nd that :
ASYNC = Real-Time Cascading (new mode in 12c)
SYNC = Non Real-Time Cascading (old mode,and the only option in 11g )
AuthorYuchong.Xu Email:vc.123@qq.com 测试文档,若有问题请及时沟通
12c Data Guard 日志传输模式
7 Redo Transport Services< Data Guard Concepts and Administration>
17 LOG_ARCHIVE_DEST_n Parameter Attributes< Data Guard Concepts and
Administration>
SR 3-16512389474
查询归档日志:
当数据库为主库的时候
:
Col dest_name format a50;
Col
DESTINATION format a50;
Set linesize 500;
select
DEST_NAME,
DESTINATION,
PROCESS,status from V$ARCHIVE_DEST where
status <>'INACTIVE';
On primary databases and logical standbys, destinations 1 through
10 default to
ASYNC
(real-time cascading).
On physical standbys, snapshot standbys, and far sync instances,
destinations 1 through 10 default to
ARCH
transport mode. (Note that
the
ARCH
attribute is deprecated; the use of
ARCH
in this situation simply
indicates non-real-time cascading.)
of 2
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