System and method for managing concurrent access to data files consisting of data entries referenced by keys comprising sequence of digits
AssigneeInternational Business Machines Corporation
InventorJonathan A. Scott
Life of this patent
Estimating the term…
Abstract
A database management system including an index with parallel read access for large amounts of keyed information. The index can be referenced for read-only access by any number of simultaneous processes in parallel with being updated by a single process where the read-only access does not involve any locking or waiting.
Claims17
A computer data storage management system for managing concurrent access to data files consisting of data entries referenced by keys comprising sequences of digits, the system including:
- means for maintaining an index to each data file comprising a digital tree structure of index nodes hierarchically arranged according to the key structure and including at least downward pointers to lower-ranking nodes or to data entries of the data files, said pointers corresponding to possible values of an index digit;
- index modifying means for modifying the index tree as necessary to reflect changes in data entries;
- change indication means for providing an indication of predetermined types of modifications of the index tree or of a part thereof;
- index search means for searching the index for a node containing a pointer to a user-supplied key in order to permit the reading of the data entry to which the user-supplied key refers;
- and
- means for examining said change indication to determine whether said index was modified by a concurrent access to the corresponding data file during the search of said index and for causing the index search means to repeat said search if a change was indicated during said search.
A method of managing concurrent access to stored computer data files consisting of data entries referenced by keys comprising sequences of digits, said method comprising the steps of:
- maintaining an index to each data file comprising a digital tree structure of index nodes hierarchically arranged according to the key structure and including at least downward pointers to lower-ranking nodes or to data entries of the data file, said pointers corresponding to possible values of an index digit;
- modifying the index as necessary to reflect changes in data entries;
- providing a change indication indicating the occurrence of predetermined types of modifications of the index tree or of a part thereof;
- searching the index for a node containing a pointer to a user-supplied key in order to permit reading of the data entry to which the user-supplied key refers;
- and
- examining said change indication to determine whether said index was modified by a concurrent access to the corresponding data file during the search of said index and, if so, repeating said search.
Dependencies are inferred from the claim text.