I still don't know if I really understand the Derby model as it seems
the transaction logs are archived when a database backup is run. So
here is a scenario:
Day 1: Backup Primary Derby (enabling logging), copy backup database
to secondary server and boot secondary server to check it is all OK.
Day 2: Backup Primary Derby DB and copy archived log files to
secondary server.
Day 3: Backup Primary Derby DB and copy new archived log files to
secondary server.
Day 4: Boot secondary Derby DB to check its OK... In theory then
the boot process will replay all the log files and the database
should be in the same state as the Primary was on Day 3 ?
Somehow I don't think this would actually work - but I will give it a
try...
Here is the scenario I am try to cater for:
24x7 realtime system needs to be relocated to another site (or needs
to have a warm standby system that can be enabled in 15 minutes or
less).
Basic approach is to have two databases running and logs from the
primary are loaded on the secondary within a couple of minutes of
them being written.
Transaction dumps on primary database are written to timestamped
files and file is renamed TRXDUMP20080206091545212_DONE.DAT once
dump write process has completed. A script checks for presence of
*_DONE.DAT files every 30 seconds and copies file to remote servers
file system (or this gets done by the dump process as well). Script
on the remote server checks for presence of *_DONE.DAT files every 30
seconds and runs a Transaction Load process on remote database to
load the dump files. At any given point in time the remote site is
always within a few minutes of the primary site.
It seems unlikely one could do this with Derby because there are no
commands to periodically dump the transaction logs or to load the
transaction logs.
Cheers
On 08/02/2008, at 7:05 PM, Knut Anders Hatlen wrote:
Duncan Groenewald <[EMAIL PROTECTED]> writes:
Thanks - the specification looks like its close to what I would like.
The model I work from is one used by Sybase (and possibly others)
where you can specify a database dump and a separate transaction log
dump at defined intervals using a script or some other programmatic
method. From what I can tell its not possible to do this with
Derby,
since you can only dump the database and not the logs. Its also
unclear how you would load a log file on its own.
What I would like to see is two additional commands added to dump
transaction logs to specified directory or file name and another
command to load a transaction log file from a specified location/
file. Ideally a transaction log file load should function much the
same way a normal user does to allow concurrent user access while
loading a transaction log file.
Not exactly what you want (it won't allow concurrent user access while
loading the transaction log), but you may achieve something similar
with
log archiving and roll-forward recovery, combined with some creative
scripts. I haven't tried it myself, but you may get some ideas here:
http://db.apache.org/derby/docs/dev/adminguide/cadminrollforward.html
--
Knut Anders
Duncan Groenewald
mobile: +61406291205
email: [EMAIL PROTECTED]
