DB2 Express is at the very bottom of the DB2 database family which includes Workgroup Server, Workgroup Server Unlimited, Enterprise Server, and Enterprise Server DPF.
|Product||IBM DB2 8.2 Express Edition|
|Price||per CPU, unlimited users $8,106, or per server $1,037.84 plus $206.24 per user.|
|Phone||13 24 26|
|Limited to two CPUs, strong features set, very good user interface, solutions for Windows and Linux.|
|This edition can handle quite a workload before you would need to move to a more powerful version. Scales with little drama all the way up to Enterprise Edition and support for clustering, failover, etc.|
|Lower cost than Oracle but Express only supports two CPUs to Oracle's four and some features are cost options.|
|Support is included in the purchase price for first year and includes 24x7 phone and e-mail support. At the end of the first year the customer has the option to renew the licence at a cost of $1,600/year/CPU or if they chose pay less for shorter support hours.|
Be careful when examining the features of the product as we found DB2 boasts many features but not all of them are standard -- in fact, quite a few are optional extras or not even available. For example, partitioning the database across multiple servers for performance and redundancy is only standard on Enterprise Server DPF.
Installation and configuration are very easy and the novice can simply walk the logical and simple path of the DB2 Wizard -- the Wizards often present multiple choices for database creation and configuration that are clearly explained and carry out much of the many and tedious configuration settings in the background. For example, during configuration we were presented with an option to tune the database performance based on usage model. Three models were presented: a transaction model, a data warehouse model, and in case these two are too confusing or if you have a mix of both in your environment, there is a third option that encompasses both.
There is no doubt that IBM's DB2 Express database features the most extensive and easiest to use file import and compatibility capabilities. The import wizard is simple to use and the import characteristics of the file can be finely tuned through a standard GUI that any novice could drive.
Another feature worth a mention is the Database Federation feature (which comes at extra cost). In a nutshell, Federation utilises "wrappers" to allow your front end to query other vendor's database applications. For example, you may have a stock management system on Sybase and an employee HR system on SQL Server -- with the corresponding wrappers DB2 Express allows your front end to seamlessly query any of the databases. The software is even smart enough to re-write SQL commands to speed up performance across the different databases.
While DB2's 512GB per table may appear a little small when compared with MySQL's 64TB for example -- you can have up to a "theoretical limit" of 32,768 tables or 16,384TB in total.
While Oracle's row locks are inviolate, the isolations levels of Express can be tweaked between allowing dirty reads (when a database allows a user to read updated data that has not been "committed" by the user inputting the data) and not allowing dirty reads with the former providing a boost in overall performance -- which path you follow depends on your requirements.
Express' lock list is maintained in RAM in contrast to Oracle's table-stored locks so in high and unusual load situations it is possible to overload the lock list buffer. This can potentially cause row locks and can escalate up to page and table locks in extreme circumstances. If this happens frequently it is obvious that you have too little RAM, but if it only happens on rare peak load conditions then you have to make the choice and weigh the added expense of the rarely utilised memory and user satisfaction. It's a sad fact that if it is busy and the locking escalates, transaction speed can plummet as greater slabs of the database are unavailable.
A feature of Express' excellent user interface is the Health Center which tracks database performance and issues Attention, Warning and Alarms in escalating severity. It is displayed in a simple graphical format where the user can drill down and investigate every instance. Hand in hand with this feature is the Design Advisor which deeply analyses the database's operational statistics and then recommends tweaks and improvements to optimise the database. This may range from advice on implanting extra indexes or dropping unused indexes, to repartitioning suggestions.
Speaking of the user interface, at first glance it doesn't appear as friendly as Oracle's but it turns out to be very easy to use and drill down. It is very powerful with a wide range of features and 14 highly desirable Wizards.
The first year of support is included in the purchase price, known as Passport Advantage Express it includes 24 x 7 phone and e-mail support. At the end of the first year the customer has the option to renew the licence at a cost of AU$1600/year/CPU or if they choose, pay less for shorter support hours.
Like Oracle, IBM has two licensing schemes. The first is based on a fixed cost per server, no matter what its capabilities, and then a cost per user. This of course would not work for an online system where the number of users is not quantifiable, so you are left in our scenario with a charge of AU$8106 per CPU and unlimited users. This appears quite reasonable although bear in mind that a lot of features that are standard with Oracle are extra cost items with DB2.
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