Data replication is not unique to Notes. However, Notes replication is unique in that the data used in Notes is not relational. The fundamental object in Notes is a document, not a relational record. A lack of relational capabilities, and the delays inherent to Notes replication schedules, make it an inappropriate database for some types of work-flow applications. These factors also make Notes unsuitable for computation-intensive applications that use relational data.
Jagdish Mirani, product marketing manager for Sybase's Replication Server, points to some of the advantages in the world of relational data. First, he says, unlike Notes, data in Sybase is modified by SQL transactions. Replication Server does not transm
it the new data; it transmits the SQL transactions that modify the data. This requires far less network traffic, especially in cases where many records are modified by a single query. This approach also significantly reduces connection times and replicates transactions within seconds of their occurrence.
Second, Replication Server provides dynamic transaction routing. The decision to determine where a specific transaction should be replicated to can be postponed until after the transaction has been registered, and it can be based on the business logic at each stage. An order-processing application provides a good example. Whenever a new order is entered, a logical query can be run on the database to select which of several distributed warehouses located around the country (or around the world) should receive the order. The decision could be made by a calculation based on predetermined parameters, such as availability of the ordered product, the proximity of the warehouse to the shipping destination, an
d other factors. Within seconds, the order is replicated to the chosen warehouse and processed appropriately.
PATCHING THINGS UP
Here's what some companies are doing to integrate relational
distributed-database products with Notes.
SYBASE'S REPLICATION SERVER
... now works with Sybase and DB2, and it should be Notes-enabled in
the fourth quarter of this year. One Notes server will function as a
Notes system's gateway to the relational world. A DLL process will
capture any change to the gateway databases and create a relational
transaction that describes the change to the data. A replication
agent will send the transactions to Replication Server. Replication
into Notes will rely on Sybase's custom ODBC (Open Database
Connectivity) driver. Initially, the only data types supported will
be numeric, text-string, and date/time.
GUPTA'S SQLBASE
...is geared for mobile users and assumes occasional connectivity to
a server to replicate selected subsets of the relational data.
SQLBase connects to Notes for data access. Replication with Notes,
however, is only in the early development stages.
INFOPUMP FROM TRINZIC
...while not a database product, provides data transfer capabilities
and an interface to roughly 20 different database products, including
Notes. It also provides replication capabilities to maintain the
synchronization of data.
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Strained Relations
