Praxis International Inc and its UK subsidiary CCA, formerly Computer Corp of America, a company slipping quietly into the mire with its Model 204 database, has made an assault on the world of data warehousing with the OmniArchitecture Series. This comprises the OmniReplicator, OmniWarehouse and OmniInfo. The advantage that a data warehouse provides is that it sits between the operational databases and the end-user to provide the user with an query-intensive database, constantly updated by the operational databases, but without compromising the performance of the operational database. Operational databases are ill-suited for end user access, great at transaction processing but lousy at queries and analysis. The addition of the data warehouse gives businesses with an installed base of mainframes a method of prolonging the lifespan of operational databases.
Replication
Mainframes can concentrate on transaction processing and forget about responding to ad hoc queries. The purpose-built data warehouse also reduces network traffic as users carry out query intensive applications on a local level. If the company is trying to migrate, the data warehouse offers the potential for a staged migration, application by application, from the mainframe to the client-server model. The data warehouse also offers high availability and fault tolerance, since if the primary database fails, the user can still access information from the up-to-date datawarehouse. Praxis claims OmniReplicator is the first bi-directional data replicator and is due in the first quarter of 1995. It provides replication between and among DB2, Oracle, Sybase and Model 204 databases. The replicator also provides one-way replication between these databases and other Open Data Base Connectivity-compliant databases, including Informix, Ingres, Sybase, Rdb, Teradata and these lists will expand in the future. It can also rationalise, ‘massage’, summarise and enhance the data without additional programming – for example making all dates conform to the same formula, so they will all appear the same to the user. It moves a copy of the source database or a subset of a source database to a set of clients and then keeps the data current through automatic refreshing. Updates on the target database can be continuous or scheduled: each time a transaction updates the source database OmniReplicator updates the clients or every hour, day or week. The OmniReplicator relies on asynchronous rather than synchronous replication. In synchronous replication all the targets are updated before the source transaction is complete, utilising a two-phase commit.
By David Johnson
This is the right approach for certain types of transaction, transferring sums of money for example, where you need to know that the money exists before you make the transferral, and credit and debit the accounts at the same time. However response times can be slow as all the target databases have to be confirmed before the transaction can be completed, network traffic is hence high and relies heavily on the strength of the system – if one of the databases to be updated is down, the whole transaction has to wait until it comes back. With asynchronous replication, the source transaction is complete when the source database is updated, without the involvement of the target databases. These target databases are then updated at a later time. Network traffic is reduced also because the only information that is transferred are the updates, not the whole files. The OmniWarehouse is a post-relational data warehouse database, designed for intensive query and analysis applications, and will be available in the second quarter of 1995. It boasts advanced indexing; file segmentation and partitioning; stored procedures; special data warehouse functions; nested tables; support for interactive queries; and multi-dimensional architecture features. The first system for the OmniWarehouse will be the IBM Corp RS/6000, with other Unix systems following plus Windows NT and MVS versions. It will also be updated to include real-time, dynamic
update capabilities. SQL 92 entry-level compliance and support for Open Data Base Connectivity-compliant personal computer tools.
Stoplight
The other part of OmniArchitecture, OmniInfo, an Executive Information System will be launched in June of 1995, and will sit at the front end of the structure. Priced at under $100 per user, the OmniInfo will provide generalised query and reporting, context-sensitive hot spots that point to further information, drill-down, stoplight charts providing exceptions and variances, trend analysis through images, pictures, maps and graphs, plus Open Data Base Connectivity for integration to other databases beyond OmniWarehouse. In its first release you will not be able to update the data warehouse through the OmniInfo, but this is promised in the future. Praxis prides itself on its database independence. Other companies offering a replication system are database vendors offering replication between their own databases and according to Praxis, William Inmon, executive vice-president of technologies at Prism Solutions Inc and the ‘father of data warehousing’, is impressed by this. He thinks that Praxis will be the only vendor in the market to offer an integrated system that combines change-data capture through heterogeneous data replication and a robust data warehousing engine. However, with the rising interest in data warehousing other companies are sure to follow.
