Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-11-24
2002-10-15
Breene, John (Department: 2177)
Data processing: database and file management or data structures
Database design
Data structure types
Reexamination Certificate
active
06466936
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 9804076-9 filed in Sweden on Nov. 26, 1998; the entire content of which is hereby incorporated by reference.
1. Field of Invention
The present invention relates to a method of regulating load in a distributed database.
In a distributed database, information entering the database is distributed between several different database nodes. A request from a user is served either by the node to which the user connects, which is here called a receiving node, or by another of said nodes that is able to meet the request, after the receiving node having forwarded the request to said other node. A node that can meet the request is here called the serving node.
2. Description of the Background Art
It has long been known that in the case of a distributed database in which information or data belonging to the database is distributed between several different nodes a user need not necessarily know in which node the requested information is found, but simply connects to a node and asks to be allowed to perform an operation in the database.
This operation may be one in which the user requires access to information in the database, or access to one or more objects therein, for instance to read the object or to write into the object.
The receiving node may itself be a serving node that can meet the request, or forwards the request to the node in the database that can deal with the request, in other words the node that includes the requested object.
It should be mentioned that there is a difference between an operation and a transaction. A transaction includes a plurality of operations, where the number of operations concerned will depend on the complexity of the transaction.
It is also known that the total executing capacity of a database is equal to the sum of the executing capacities of all the nodes in the database. When requests are made to the various nodes and these requests need to be distributed between said nodes, hot spots are liable to occur which overload one node whilst leaving other nodes spare capacity, despite the fact that the total capacity of the database has not been used to the full.
Several different methods of solving this problem are known to the art, these methods normally being referred to as load regulating methods.
Prior Publication U.S. Pat. No. 5,450,584 teaches a load regulating method where an internal load monitoring unit in each node monitors the extent to which the own node is loaded, and an external load monitoring unit in each node that monitors the extent to which each other node is loaded. A central unit for handling the load distribution within the database is connected to each unit for load monitoring purposes.
The central load distributing unit functions to shift information from a node which, via its internal load monitoring unit, indicates that the internal node has exceeded a highest permitted level, to a selected other node in the database. This movement of information, often requested information, from a heavily loaded node to a less loaded node results in more uniform distribution of the load between the nodes in the database.
Prior Publication EP-A2-0 642 092 teaches a method of regulating the load within a parallel database system. Load distribution is governed by the way the information in the database can be redistributed from an active node to a new node or to an unused node.
This method is thus also based on the redistribution of information in the database between the nodes included therein.
Prior Publications U.S. Pat. Nos. 5,551,027, 5,379,424, 5,668,986 and 5,606,693 describe further methods for regulating the load in distributed databases or distributed information within a computer system.
SUMMARY OF THE PRESENT INVENTION
Technical Problems
When considering the present state of the art as described above, it will be seen that a technical problem resides in enabling the load between the nodes of a distributed database to be regulated in the absence of a central function that monitors the load on the nodes in said database or which handles the total load regulation therein.
A further technical problem is one of providing a load regulating facility that requires no co-ordination between the database nodes, but which can be implemented and handled locally in respective nodes.
A further technical problem is one of providing a load regulating facility that regulates the load between the nodes in the database without needing to re-distribute the information content of said database between the different nodes to this end.
Another technical problem is one of regulating incoming requests to each node in a manner that will ensure that the total number of requests to the database will not exceed its total execution capacity.
Yet another technical problem is one of enabling such limitation to be related to the number of requests that are allowed to enter the database via each individual node.
A further technical problem is one of providing requests with a waiting option when load regulation has shown that a request cannot be permitted because of the danger of overloading the database.
In this respect, a technical problem is one of limiting the request waiting time, and therewith the database response time, when a request cannot be allowed because of the danger of overloading the database.
Another technical problem is one of ensuring that no hot spots will occur in the database, and that this assurance can be upheld in a database that includes nodes of different executing capacities.
When a transaction requested by a user can be divided into a number of operations, and when each commanded operation is comprised of a request, a technical problem resides in ensuring that requests belonging to a transaction that has already commenced can be met so that ongoing transactions can be completed and need not be discontinued or aborted.
Another technical problem is one of enabling a database to be load-regulated with a starting point from the number of incoming requests, where each request comprises a command operation.
A further technical problem is one of enabling the load on a database to be regulated with a starting point from the execution cost incurred by respective requests.
Still another technical problem is one of allotting a relevant execution cost to respective requests.
When no more requests can be permitted through a specific receiving node and when other nodes are able to permit more requests to be undertaken in their capacity as receiving nodes, a technical problem resides in still enabling the specific receiving node to receive more requests.
Another technical problem is one of handling a request that comprises an operation which can be divided into several parts, such as a review of the entire database or a review of parts thereof, when the receiving node and/or one or more other nodes do have the capacity to meet the request.
It is then also a technical problem to handle a request that comprises an operation which can be divided into several parts, such as a review of the entire database or a review of parts thereof, when the receiving node and/or one or more other nodes do not have the capacity to meet the request.
Solution
With the intention of solving one or more of the aforesaid technical problems, the present invention takes as its starting point a distributed database where information within the database is distributed between several different nodes belonging to said database, wherein a user request is served either by the node to which the user connects, here referred to as a receiving node, or by some other node after the receiving node has forwarded the request to one of those nodes capable of meeting the request, these nodes being referred to as serving nodes.
With the intention of providing a method of regulating the load in such a database in which no central controlling or monitoring facility is used with respective nodes, it is proposed in accordance with the invention that respective nodes are allocated one or more key-numbers which function to limit the nu
Breene John
Pham Linh M
Telefonaktiebolaget L M Ericsson (publ)
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