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A Structure for Concurrent Operations on

Statistical Data

**F. Wu, J. K. Chen and Y. H. Chen**

National Tsing Hua University

Hsinchu, Taiwan 300, R.O.C.

TBSAM^{link}, a variant of TBSAM, is an access methods for processing aggregate queries in a multi-user environment. Designs are made of deadlock-free operations which search and/or update a single data node or a range of data nodes. The correctness of these concurrent operations and the deadlock-free property are proved. When the techniques of *right-link*[14], *lock-coupling*[13], and the proposed *rechecking* are used to update the value in a single data node, at most two nodes are required to be locked. For updating a range of *r* (*r*>1) data nodes, at most *r*+1 nodes (*r* data nodes and one non-leaf node) should be locked. To evaluate the efficiency of these concurrent operations, mathematical formulas for the number of nodes to be accessed and/or locked are derived.

Keywords: aggregate query, concurrent operations, range updating, rang reading

Received Sepbember 27, 1993; revised February 23, 1994.

Communicated by Wei-Pang Yang.
^{*}This work was supported by the National Science Coucil under Grant NSC82-0406-E007-243.