2. Knowing When a Copy Is Complete
The question then becomes, how
do you know the copy is finished? The answer is that Microsoft created a
new data management view (DMV) to return the details of the database
copy operation. This DMV is called sys.dm_database_copies, and it
returns a great deal of information about the status of the database
copy, such as when the database copy process started and completed, the
percentage of bytes that have been copied, error codes, and more. In
addition, Microsoft modified the state and state_desc columns in the
sys.databases table to provide detailed information on the status of the
new database.
Figure 2
was generated by deleting the TechBio2 database and creating it again.
This time, a statement looks at the sys.dm_database_copies DMV and
checks the status of the copy. You can see the statement highlighted in Figure 2.
You can also see results in the figure from the query against the DMV.
The TechBio database was tiny to begin with, so the copy takes only a
few seconds, if that.
3. Automating a Database Copy
You can schedule a database
copy via an on-premises SQL Agent job and an SSIS package (as discussed
earlier in this chapter). The job can be scheduled like a normal
on-premises SQL job, as long as the connection information for the
Execute SQL task points to the SQL Azure database.
Although this may not be
the most favorable solution, it's certainly an option, and it does
provide the scheduling capabilities you're looking for. The key for this
solution is to first delete the copy database before you re-create it.
4. Maintaining a Backup History
The Database Copy
functionality lets you create an instant backup of your database, but it
doesn't provide a way to create a backup history. In other words, you
can't append to the backup and create multiple days' worth of backups.
You do have several options, however.
If all you care about is
backing up the current day's data, you can delete the current backup
copy and re-copy the database. This is a viable option and doesn't
require a lot of maintenance.
If, on the other hand, you
want a backup history, doing so is a bit more tricky. Many, if not most,
companies like to keep a week's worth of backups. These companies back
up their databases each night and keep seven days' worth of backups so
they have the option to restore past the previous night's backup. To do
this with the Database Copy functionality, you must create seven copies
of the source database—you have seven backup copy databases.
This strategy works, but
keep in mind that you're billed for those additional seven databases.
The key here is that if you're using SQL Azure, a look at your backup
plan is critical.
What does Microsoft have
coming in future Service Updates? The company is working very hard on
adding and improving SQL Azure backup and restore functionality.
Microsoft wants to hear from you—your feedback is important. Talks of
database cloning and continuous backups have surfaced; keep your fingers
crossed that this functionality and more will appear in the near
future.
