Re: Informix replication doesn't....

On Mon, 18 Jul 1994, Bill Duncan wrote: > > I heard the following about Informix's replication capabilities in the v6.+ > and was wondering if I could get any confirmation either way from the net. > > (1) The primary and secondary site hardware must be the same, or atleast > offer identical paging structure. True, Informix state that the primary and secondary must have the same *port*, not just version. This would dictate that hardware and paging structure be the same. The Admin guide for 6.0 DSA also states that the o/s must be the same. > > (2) The OnLine config. on both the primary and secondary sites must be set up > exactly the same. Not completely, Dbspace, Physical-Log, Logical Log and Shared Memory Configurations must be the same, but variations in areas such as Mirroring and Tape devices are allowed. > > (3) You can only have one secondary site per primary site, i.e. a 1:1 > correspondence between primary and secondary sites. True. > > (4) Secondary sites are read-only. > True during replication. > (5) From the secondary site, you can not determine if a failure is at the > primary site itself or a failure of the network. Not sure. > > (6) Launching the entire replication process is difficult because both sites > have to be kept closely in sync. > Not sure, to launch replication a level 0 archive of the primary site must be applied to the secondary site. Once the two sites have established a data-replication connection the secondary site will use the logical logs from the primary site to roll-forward to a point of consistency. Seems fairly straightforward. I have never attempted DR on a site with a high OnLine load, though. > (7) There are no administrative tools, just a few variables that can be > queried or set to direct some of the replicate process behavior. onmode/ontape/onmonitor seem to do the job > > (8) There is no mechanism for resolving inflight transactions that do not > make it to the replicate site in the case of a hot-site backup scenario. Re- > syncing the primary site after it comes back on-line is not possible without > heavy manual intervention. > True if the secondary site becomes the Standard server. > (9) High transaction rates on the primary replication site can cause the log > to grow to fast for replicates to keep up....the result is loss of data from > the logs. > No Idea. > > I know that everybody else's replication approach suffers from some if not > all of these problems, but most of these I heard at LAST YEARS Informix User > Conference (couldn't afford to go this year) from the Informix product > manager. I was just wondering if things had changed and if anyone in the > know could shed some light on these issues. > > Bill Duncan Hope this helps, BTW, just to confirm my understanding I pulled the System Admin guide for 6.0 DSA, and I found this line : "It is also important for the OnLine administrators of both the database servers to communicate when performing administrative tasks (for example by telephone)". Never! :-) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mark Lansley <mark@dsl.com> | "Whoa!....Maybe I'll just pass Druid Systems Ltd, UK | on my usual barking frenzy." +44 932 571212 (Vce) 571552 (Fax) | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~