Figure 8-5. When all is well with database mirroring, the mirror database should appear
as synchronized and restoring.
CHAPTER 8 n DATABASE MIRRORING 198
If, for some reason, the mirror is still in a state of ???synchronizing,??? that means it??™s not
identical to the principal and is in the process of receiving new data. This can happen
when database mirroring is first established, or if mirroring is set to run in an asynchronous
mode and the mirror database is in the process of catching up.
In the event that a principal database fails but the mirror remains available and database
mirroring is not configured for automatic failover, the mirror database will show as
disconnected, as you can see in Figure 8-6.
Figure 8-6. Remember, the mirror database should always be either restoring or in
recovery??”never simply online.Once the mirrored database is online, it??™s the new principal!
If you attempt to access the database mirroring properties in SSMS for the witness
database while the principal was down or unavailable, you will receive the error shown
in Figure 8-7.
Figure 8-7.
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