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<p><b>Abstract</b>—We consider a variant of B<super>+</super>-tree called the <it>B</it><super><it>+</it></super>-<it>tree with physical clustering</it> (BC), which is exemplified by VSAM key-sequenced datasets. In this file, logically contiguous data buckets are physically clustered in a storage unit called a <it>region</it> in order to enhance the efficiency of sequential processing. As a consequence, records in a bucket are redistributed over time according to two different split algorithms: <it>bucket split</it> and <it>region split</it>. A stochastic model of the disorganization of BC files is constructed using order statistics. Database administrators of on-line transaction systems often need to reorganize BC files before a region split occurs. An efficient algorithm for determining the optimal reorganization time of BC files is developed. Analytic results are validated by simulation. In passing, we discuss guidelines for load-time configuration of BC files.</p>
B+-tree, dynamic indexed files, physical database, VSAM, stochastic model of file dynamics, file reorganization, order statistics, simulation.

V. Sridhar and J. S. Park, "Probabilistic Model and Optimal Reorganization of B+-Tree with Physical Clustering," in IEEE Transactions on Knowledge & Data Engineering, vol. 9, no. , pp. 826-832, 1997.
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