In my previous post, I showed which IBM products contain Q and SQL Replication. However, I left one question unanswered. What's the difference between InfoSphere Replication Server and the IBM Homogeneous Replication Feature (HRF)? The answer is simple. The HRF is just a tool to license a subset of Replication Server found in DB2 Enterprise and InfoSphere Warehouse.
The HRF was introduced with DB2 9.5 and provides what's shown in the following table.
|Product||SQL Replication||Q Replication|
|InfoSphere Replication Server|
|IBM Homogeneous Replication Feature|
In other words, Replication Server provides Q and SQL Replication for all types of databases - DB2, Oracle, and so on. That diversity of databases is what's called 'heterogeneous' replication. On the other hand, the HRF is a way to buy just the subset of Q Replication that's for DB2 databases. This subset is called 'homogeneous' because it licenses components for only one type of database - DB2.
This functional difference also means the HRF has a cheaper per PVU price. Or at least it still did when I started this post :) If you want to verify this yourself, check Passport Advantage or go to the product web pages on ibm.com and look at the features of DB2 ESE and the prices for Replication Server.
A related difference is that the HRF really is a feature instead of a product. As such, it can be purchased for any of the following IBM products:
- DB2 for Linux, UNIX, and Windows*
- InfoSphere Warehouse*
- The IBM Smart Analytics Systems - models 5600 and 7600* as well as the new 7700*
*Yes, SQL Replication for DB2 databases is provided at no additional cost in these IBM products.
This feature aspect also affects how you calculate the total cost of a replication purchase. Specifically, there is a metric called Processor Value Unit (PVU mentioned above) that is a factor in determining the overall price of a replication purchase. The metric is calculated differently for the HRF than for Replication Server.
- For the HRF, the metric is the same as the PVU count for the database for which the feature is purchased.
- I've always been told that DB2 features are based on the same PVU count as DB2 and are not charged for on warm standby systems. (DB2 people are always the best ones to verify the current state of charges for DB2 features.)
- There is no requirement to count the PVU of remote source or target databases (if you do remote capturing or remote applying with the HRF).
- For Replication Server, the metric is based on the system where the software runs, not the PVU rating of any source or target database.
The last point here is that Replication Server and the HRF are completely compatible. In other words, the Capture program in one can provide changed data to the Apply in the other and vice versa. The following picture is a very simple example that illustrates the compatibility of the two.