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  Mobile Users Stay Connected Via Tactica Caprera, The First Offline TP Monitor |
By Barry Nance
 You can see the need for transaction processing monitor middleware when you visualize an application so heavily used that it requires multiple database and application servers to support a large user population.
A TP monitor helps the many application instances on the various servers coordinate, balance the workload and ensure database integrity. However, TP monitors assume each client has a persistent connection to the network. But what about mobile users who need to temporarily work offline? How can salespeople on the road issue sa les orders and returns, for instance, against an unconnected database and later apply those transactions when they return to the main office? The solution to these users' problems is another kind of middleware, the offline TP (OFTP) monitor.
True OFTP monitors are sophisticated enough to combine replication, message queuing, security and conflict-resolution functions. Oracle Corp.'s Mobile Agents, Radnet's WebShare, Synchrologic's SyncKit and XcelleNet's RemoteWare are the closest competition to OFTP monitors, but these products lack conflict-resolution functions . Some corporate software engineers, likely discouraged by the dearth of OFTP monitor middleware products, have painstakingly created homegrown solutions for their companies' temporarily offline workers. Other businesses, terrified by the possibility of inconsistent databases, have let their fear dictate awkward, unrealistic business procedures. Tactica to the Rescue One software tool does exist in the OFTP monitor middleware category: Caprera Mobile from Tactica Corp. We expect others in the future, and database and TP monitor vendors eventually will incorporate OFTP monitors into their products. Microsoft, for instance, says it plans to offer support for mobile clients in the new 7.0 version of SQL Server, now undergoing beta tests. It contains support for mobile clients, including replication, message queuing and conflict-resolution mechanisms. For now, however, Caprera Mobile is the only commercial alternative. The package Tactica sent us was named simply Caprera, but, just as we finishe d testing, Tactica tacked the qualifier "Mobile" onto its name. Caprera claims to supply a database infrastructure and conflict-resolution mechanism for temporarily offline workers. To explore its capabilities and determine its usefulness, we put Caprera through its paces, issuing updates (consisting of sales, returns and restockings) against an inventory database of goods for sale. We used SQL Server 6.5, running on Windows NT Server 4.0, to store our inventory of widgets. A small Visual Basic 5.0 program that we wrote provided the widget sales user interface. Tactica says you can use any programming language that supports ODBC (Open Database Connectivity) and ActiveX. The program accessed local database content via ODBC and used Caprera's ActiveX components to synchronize that content with the central database.
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OFTP monitors don't take the place of TP monitors like BEA Systems' TUXEDO, IBM Corp.'s Transaction Server or Microsoft Corp.'s Transaction Server. Rather, OFTP monitors let users take portions of the database offline, update those segments and later apply these changes against the central database. If deferred transactions cause database anomalies, the OFTP monitor can resolve those conflicts.
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