Other ERP articles:
ERP Testing ERP Business Analysts ERP Contracting ERP Data Migration ERP Reasons to Get One ERP Forces Changes in Business Rules ERP One ERP is the same as any other ERP ERP Security is OXYMORON ERP The Whole is Bigger than the Parts
What is the difference between ERP software products? Why choose one over the other? Well from my view they are all the same. An big fat fugly application layer with a proprietary language and referential integrity enforced in this layer. This sits like a fat lady on the skinny horse that is the underlying RDBMS, usually DB2, Informix or Oracle. Domain constraints except for datatype are virtually unused. Referential constraints are also unused. Datatypes in the application layer may include arrays, and is not a normalized model but translated into bare tables in the RDBMS.
The basic fact is that these systems are not relational data models, just a complex hodge-podge of the legacy file based systems from which they evolved.
This makes an unstable set of data that easily loses its integrity. ERPs are dependent on the programmers of its arcane proprietary languages to do the management of data that most RDBMS can do more efficiently. Logical transactions, even indexes are convoluted or missing in some ERP systems. Batch job restart or commit points to resume long transactions are crude or missing also. Configuration management of the software is a complex maze of intricate rules. The data model is vast with thousands of tables. Metadata is lacking or written in GERMAN (SAP), DUTCH (Baan), or entirely missing in ENGLISH (PeopleSoft). This results in a system that is barely manageable, many times dozens of patches are released a month, but the data integrity problems make testing applying and releasing patches a major chore for configuration management. Most of the ERPs have had crude or non-existing configuration management for patching and upgrades, the testing of patches and upgrades is also a major difficulty.
In the history of these twisted systems are ports to Unix from the world of rusty iron mainframes and file based data stores without an underlying RDBMS. As a result of this porting they bring with them many of the old problems and few of the new solutions.