Re: Transaction-controlled robustness for replication

Hi,

Simon Riggs wrote:
> Classification of Replication Techniques

Thanks for your classifications. It helps a great deal to clarify.

> Type 2 is where you ship the WAL (efficient) then use it to reconstruct
> SQL (flexible) and then apply that to other nodes. It is somewhat harder
> than type 1, but requires less infrastructure (IMHO). Definitely
> requires less data shipping from Primary node, so very possibly more
> efficient.

What leads you to that conclusion? AFAICT a logical format, specifically 
designed for replication is quite certainly more compact than the WAL 
(assuming that's what you mean by "less data").

The only efficiency gain I can see compared to type 1 is, that most of 
the processing work is offloaded from the master to the slave(s). For 
setups with multiple slaves, that's a bad trade-off, IMO.

> Previously, most RDBMS vendors supported type 1a) systems. They have now
> moved to type 2 and 3 systems. Both DB2 and Oracle support a type 2
> *and* a type 3 replication system. The reasons they do this are valid
> for us also, so I suggest that we do the same. So for me, it is not
> about whether we do type 2 or type 3, I think we should do both.

I currently don't think type 2 is doable with any reasonable effort, but 
hey, I'm always open for surprises. :-)

Which of IBM's and Oracle's products are you referring to?

Regards

Markus Wanner