Recently, spatial databases have attracted increasing interest in the database field. Because of the volume of the data with which they deal with, the performance of spatial database systems' is important. The R-tree is an efficient spatial access method. It is a generalization of the B-tree in multidimensional space. This thesis investigates how to improve the performance of R-trees. We consider both parallel I/O and centralized architectures.

For a parallel I/O environment we propose an R-tree design for a server with one CPU and multiple disks. On this architecture, the nodes of the R-tree are distributed between the different disks with cross-disk pointers ( 'Multiplezed R-tree a). When a new node is created we have to decide on which disk it will be stored. We propose and examine several criteria for choosing a disk for a new node. The most successful one, termed 'Prozimity Indew' or PI, estimates the similarity of the new node to other R-tree nodes already on a disk and chooses the disk with the least degree of similarity.

For a centralized environment, we propose a new packing technique for R-trees for static databases. We use space-filling curves, and specifically the Hilbert curve, to achieve better ordering of rectangles and eventually to achieve better packing. For dynamic databases we introduce the filbert R-tree, in which every node has a well defined set of sibling nodes; we can thus use the concept of local rotation [47]. By adjusting the split policy, the Filbert R-tree can achieve a degree of space utilization as high as is desired. (Also cross-referenced as UMIACS-TR-94-131)