Synchronization can be unidirectional or bidirectional. In most
cases, you will use bidirectional synchronization.
Unidirectional synchronization is suitable in situations like these:
You use a replica as a backup.
Your company supplies information to another site (or company) for read-only
use.
A high-security development project uses the same data as a more open
project. In this case, the open project sends updates to the high-security
project, but no updates are sent in the other direction.
Figure 1: Unidirectional and
bidirectional updating
Unidirectional updates carry some risk. For example, an accidental
change of mastership cannot be fixed, and restoring from a replica that does
not exchange updates directly with the broken replica involves extra work.
Also, you must ensure that no work is done accidentally in a read-only replica; you can do this by creating
triggers, or locking the VOB.
