""Joshua D. Drake"" <jd@commandprompt.com> wrote in message
> > 5. There will be a 2 tier replication
> > only for committed data transfer asynchronously
>
> Could we get more description on this?
>
We used Ora7.x workgroup edition that did not have replication
so we wrote the required routines
What we wanted:
Each site's data is independent and must only reflect at other sites
(i.e. a copy placed at each other sites) There can be a latency and
it will be a two-tier system (1 grand parent, several parents and each
parent
to have several children)
Each parent & its children will have common data
Grand parent will have all the data, some data from each parent
to be redistributed to all other parent sub-systems
How we implemented (specific only to oracle with limitations as
stated before, to be totally redone in Postgres scenario)
- Triggers on each table maintain in a separate log-table - records
of rows that are added / modified / deleted (alongwith old values)
- A generic routine would loop thru the log creating an sql for
insertion / updation / deletetion for the row
- The sql is sent to the other site and fired duplicating the effect
- A site is dedignated as the parent site, all remotes send the SQL to
the parent site whch in turn returns to each remote site
eventually all data is duplicated at all sites
- The system has a lot of safety checks & recoveries for failed transfers
missing etc and has been in operation of 7 years in volumes above
- All this was 1 tier, 1 parent with several children no grandparent
now we also require 2 tier, 1 grand-parent, several parent subsystems
Regards
Sanjay Jain
www.minisoftindia.com
