* Replication used here is namely “Real-time” Asynchronous Replication
Production Env.
DR Env.
WAL will be sent to DR Env.
at the same time of writing
WAL to the storage in
Production Env.
2’. Send
WAL
1. Commit
DB Server
DB Server
Application
3. Confirm
2. Write
WAL
Write WAL
SAN Storage
SAN Storage
DB
DB
(business data)
(business data)
In-flight data can be lost in
case disaster happens
before [2’. Send Write Log]
is complete.
[Legend]
Synchronized transaction
Asynchronized transaction
* Diagram aims to explain data replication sequence.
* Redundancy as well as unnecessary components are not shown in diagram.
Source: Preparatory Survey Team
Figure 3-23 Data replication (asynchronous replication by database)
(C) Configuration Option
There are two options for system configuration at the DR site. A redundant
configuration is better than a non-redundant configuration.
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