Re: replication

Maria L. Wilson wrote (in two similar posts): > I am interested in the functional differences in CDR (Continuous Data > Replication) and ER (Enterprise Replication). > > Our site (Informix 7.23,Solaris 2.5.1 on Sparc Enterprise 3000's) is > looking at a primary web server and a primary database server with high > availability on the two servers. The basic need for the replication of > DB is for the "high availiablity" in case one server is down the > information can be obtained automagically from the other server without > delay. > > I would be interested in any doc's or url's that are good references to > the specs on these products. and > Can someone tell me what tools that Informix has available for data > replication in version 7.23? I know of CDR (continuous data > replication), HDR (high availablity data replication) and ER (enterprise > replication). Are some of these products version specific? > > I am looking for a replication product to support a primary and > secondary server to create a "hot backup" scenerio. > > Can anyone give some greatly needed advice? Maria, Informix OnLine (both ODS and OWS) has two types of replication rechnology. HDR (High-availability Data Replication) and ER (Enterprise Replication - previously known as Continuous Data Replication). In fact OWS has a cut down version of ER called Workgroup Replication (WR). HDR effectively 'mirrors' and entire OnLine database server on another machine. The primary server is read/write and the secondary (mirror) server is read-only. If the primary fails, you can switch the secondary to read-write mode, reconnect clients and continue working. HDR works by shipping logical log buffers from primary to secondary. It does not support non-logged databases nor BLOB columns that are stored in blobspaces (as opposed to in-table). HDR is simple to set up and operate and can operate in synchronous or asynchronous modes. It requires the primary and secondary to be identical in many respects (hardware type, OS version, OnLine version, OnLine disk configuration etc.). ER (and WR) is a very different product. It is a table level (in fact table subset level) replication product that supports multiple servers participating in each replication. Each replicate defintion can be update anywhere or master/slave (primary/target) or indeed a hybrid of these. It is a multi-threaded, parallel subsystem within OnLine. It has many features to support many different replication models. Because it is much more sophisticated than HDR, it is a little more complex to set up and administer. HDR has been available since OnLine 6.0, ER/WR is available in all ODS/OWS versions from 7.22 onwards. HDR and ER/WR cannot interoperate, not can you use both at the same time. A full description of HDR can be found in the OnLine System Administrator's Guide. Details about ER/WR can be found in the Enterprise Replication User's Guide. Both these should be delivered with the Unix 7.23 server software and also be on the CD that comes with it. I also have a detailed Technology Briefing which I wrote on ER/WR. If you would like a copy let me know and I will e-mail it to you (it is in MS-Word 7.0 format). Regards, Chris -- Chris Jenkins (chrisj@informix.com) Advanced Technology Group >>> All statements and opinions are mine and should in no way <<< >>> be construed as representing those of Informix Software <<<