Is the new version of Informix Corp’s XPS 8.1 parallel database for TruCluster configurations of Digital Equipment Corp’s TurboLaser Unix servers a truly clustered product, asks this weeks issue of our sister newsletter Unigram.X? Not according to bitter rivals Oracle Corp. The new version, which ships this month, apparently treats a cluster as two separate machines, with effectively two databases running, compared with just a single copy of Oracle Parallel Server on DEC TruCluster systems. Oracle says it means Informix users get a lot of backchat as the two or more databases are kept in synch by XPS code, implying a significant performance hit. If a customer table is split over nodes, the simplest of transactions, for example, ‘update every row in the customer table’, can involve complex transactions says Oracle, which makes use of DEC’s Distributed Lock Manager, enabling it to treat the two machines as one. We don’t split data across nodes, we run on a shared disk.Informix is like a two-phase commit, a distributed transaction between databases. Informix is benchmarking XPS on TruCluster and says instead of using a global distribution locking model as provided on DEC clustered systems, the database holds locks locally, spreading the directory caches throughout the system, partitioned amongst the nodes. This frees up network bandwidth, it argues. The company is scornful of the Oracle-DEC TPC-C benchmark figure of 30,390 tpmC, and has claimed it will achieve up to 50,000 tpmC in the same configuration. DEC’s Distributed Lock Manager software was developed by DEC specifically to enable Oracle over TruCluster, Informix says.
