Interactive enquiry system
First Claim
1. In an interactive enquiry system of the type comprising a host data processor, a central data store controlled by the host processor and adapted to store a data base, a plurality of local subsystems connectible to the host processor, each local subsystem including a local data processor for controlling access to the host processor and a local data store comprising a random access memory and a magnetic disk file connected to the local processor and adapted to store part of the data base, at least one enquiry terminal in each local subsystem connected to the local processor for accessing any accessible item in the data base stored in the central store,wherein the random access memory portion of the local data store is divided into a first part adapted to store items accessed from the data base and a second part adapted to store a directory entry for each item stored within the first part, each directory entry containing a count which is an indication of the frequency of use of its associated item, said local processor updating said count whenever its associated item is used, said local subsystem further comprising:
- means operable when said first part has no space for a newly accessed item to scan the directory entries and determine the least frequently used items, and;
means responsive to said scanning means to delete at least one of said least frequently used items to create sufficient space for the newly accessed item.
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Abstract
Described is an interactive enquiry system in which a complete data base is contained at a host computer. Local terminal sub-systems are remotely connected to the host with each local sub-system containing a local data base. Each local data base is dynamically maintained so that the most frequently used pages are retained in local storage. If storage space needs to be created, the least frequently used pages are discarded from the local data base.
423 Citations
11 Claims
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1. In an interactive enquiry system of the type comprising a host data processor, a central data store controlled by the host processor and adapted to store a data base, a plurality of local subsystems connectible to the host processor, each local subsystem including a local data processor for controlling access to the host processor and a local data store comprising a random access memory and a magnetic disk file connected to the local processor and adapted to store part of the data base, at least one enquiry terminal in each local subsystem connected to the local processor for accessing any accessible item in the data base stored in the central store,
wherein the random access memory portion of the local data store is divided into a first part adapted to store items accessed from the data base and a second part adapted to store a directory entry for each item stored within the first part, each directory entry containing a count which is an indication of the frequency of use of its associated item, said local processor updating said count whenever its associated item is used, said local subsystem further comprising: -
means operable when said first part has no space for a newly accessed item to scan the directory entries and determine the least frequently used items, and; means responsive to said scanning means to delete at least one of said least frequently used items to create sufficient space for the newly accessed item. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In an interactive enquiry system of the type comprising a host data processor, a central data store controlled by the host processor and adapted to store a tree structured data base, a plurality of local subsystems connectible to the host processor, each local subsystem including a local data processor for controlling access to the host processor and a local data store connected to the local processor and adapted to store part of the data base, at least one enquiry terminal in each local subsystem connected to the local processor for accessing any accessible item in the data base stored in the central store, the method of concentrating most frequently used pages of said tree structured data base toward one end of a page buffer in a random access memory portion of said local data store comprising the steps of:
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(1) determining if sufficient space exists in said page buffer to store a page retrieved from said tree structured data base at said host processor and proceeding to step 5 if sufficient space exists; (2) determining if the number of pages in a first push down stack of pages within said page buffer exceeds a predefined minimum number and proceeding to step 4 if said minimum is not exceeded; (3) deleting the bottom most page from said first push down stack and proceeding to step 1; (4) deleting the bottom most page from a second push down stack of pages within said page buffer and proceeding to step 1; (5) adding said retrieved page to the top of said first push down stack if the page level number of said retrieved page is above a predefined threshold number and adding said retrieved page to the top of said second push down stack if said page level number is below said predefined threshold number.
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Specification