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Freeze online backup demo
=========================
This demo helps you experiment with Berkeley DB's hot backup
capabilities, and shows how to configure Freeze to support hot
backups.
The client program is very simple: it creates an Int to Long Freeze
map, with 10000 elements. The client uses a transaction to update all
the elements with the current date-time (as a number of milliseconds
since the epoch -- 01/01/1970 at 00:00:00 UTC). It also verifies that
the old values are all the same.
This program runs forever: you need to kill it (e.g., with CTRL-C) to
terminate it.
db utility names
----------------
The Berkeley DB utilities are usually named db_hotbackup, db_archive,
db_recover, etc. If you use the Berkeley DB 4.6.21 RPMs provided by
ZeroC, the utility names are db46_hotbackup, db46_archive, etc. Please
adjust the instructions below accordingly.
Backup
------
While the program is running, you can perform a hot backup with the
backup shell script (on Unix/Linux) or batch file (on Windows).
These two scripts illustrate how to use the Berkeley DB db_hotbackup
utility. For a full description of db_hotbackup, please refer to:
http://www.oracle.com/technology/documentation/berkeley-db/db/utility/db_hotbackup.html
The following command creates a full backup (both data and log files)
in the 'hotbackup' directory:
$ ./backup full
Or on Windows:
> backup full
Alternatively, you can perform an incremental backup, which only moves
and copies log files to the hotbackup directory:
$ ./backup incremental
Or on Windows:
> backup incremental
Note that the Ice configuration file (named config) disables the
automatic deletion of old log files:
Freeze.DbEnv.backup.OldLogsAutoDelete=0
The file also sets DbPrivate to 0 to allow db_archive to access the db
environment while the client is running:
Freeze.DbEnv.backup.DbPrivate=0
The db/DB_CONFIG file is used to put the data files and log files in
different subdirectories, which simplifies archiving.
Recovery
--------
After a successful backup, the hotbackup directory always contains
a full backup that is ready to use. To switch over to this backup, you
only need to do the following:
1. Make sure the client is not running.
2. Move the old 'db' directory out of the way:
$ mv db db.old
Or on Windows:
> move db db.old
3. Move or copy the hotbackup directory to db:
$ cp -R hotbackup db
Or on Windows:
> xcopy /s hotbackup db\
If you have recent uncorrupted log files in your original db
directory, you can also copy these log files over your restored log
files and perform a catastrophic recovery to recover these updates.
With the example above:
$ cp db.old/logs/log.* db/logs
$ db_recover -c -h db
Or on Windows:
> xcopy /y db.old\logs\log.* db\logs
> db_recover -c -h db
Finally, restart the client.
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