Telecom databases are databases used in the operation of the telecom network and as parts of applications in the telecom network. The first telecom databases were Service Control Points (SCP) in intelligent Networks. These provided mostly number translations for various sevices, such as Freephone. Also databases that kept track of the mobile phones (Home Location Registers, HLR) for mobile telecommunications were early starters. SCPs and HLRs are now becoming the platforms for service execution of telecommmunication services. Other telecom databases are used for management of the network, especially for real-time charging information. Many information servers, such as Web Servers, Cache Servers, Mail Servers, File Servers are also becoming part of the telecom databases.

These servers have in common that they all have to answer massive amounts of rather simple queries, that they have to be very reliable, and that they have requirements on short response times. Some of them also need large storage and some needs to send large amounts of data to the users. Given the requirements of telecom applications an architecture of a Parallel Data Server has been developed. This architecture contains new ideas on a replication architecture, two-phase commit protocols, and an extension on the nWAL concept writing into two or more main memories instead of writing to disk at commit. The two-phase commit protocol has been integrated with a protocol that supports network redundancy (replication between clusters).

Some ideas are also described on linear hashing and B-trees, and a data structure for tuple storage that provides efficient logging. It is shown how the data server can handle all types of reconfiguration and recovery activities with the system on-line. Finally advanced support of on-line schema change has been developed. This includes support of splitting and merging tables without any service interruption.

Together these ideas represent an architecture of a Parallel Data Server that provides non-stop operation. The distribution is transparent to the application and this will be important when designing load control algorithms of the applications using the data server. This Parallel Data Server opens up a new usage area for databases. Telecom applications have traditionally been seen as an area of proprietary solutions. Given the achieved performance, reliability and response time of the data server presented in this thesis it should be possible to use databases in many new telecom applications.