B+树阶数m的最优选取

本文指出对普通的B^ 树作了一定的限制后，当选择B^ 树适当的阶数m时，对B^ 树索引文件的时间和空间利用率有一个最优的设计过程，分别给出了应用在两种数据库系统模型中的B^ 树索引文件结构：（1）具有有限内存的数据库系统（Database Systems with Limited Amount of Main Memory,简称为DBSLAM），在DBSLAM模型中，我们只是缓存B^ 树中的部分结点；（2）具有极大内存的数据库系统（Database Systems with Very Large Amount of Main Memory，简称为DBSVLAM）,在DBSVLAM模型中，我们将缓存B^ 树中所有的结点，基于以上两种模型，我们分别建立了两个不同的时空开销模型，并以此进行了优化设计。

OPTIMIZATION OF THE B+ - TREE ORDER m

Optimization is proposed of a designing procession for using the conventional B - tree while it is limited and a suitable order m is chosen. Here we will discuss the optimization under two different models of database systems: Database Systems with Limited Amount of Main Memory (DBSLAM) and Database Systems with Very Large Amount of Main Memory( DBSVLAM). In the model of DBSLAM, we store only a part of nodes of B - tree and build a model of using time - space. In the model of DBSVLAM, we store all of the nodes of B - tree and build a model of using time - space.Basing on the two models,the mathematical methods for optimization are also presented.