Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-06-09
2001-09-04
Lane, Jack A. (Department: 2185)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S016000
Reexamination Certificate
active
06286113
ABSTRACT:
BACKGROUND OF THE INVENTION
In digital communications networks, particularly in SDH networks (SDH=Synchronous Digital Hierarchy), a database containing data about the current network configuration is provided for each network element. Network elements are also referred to as “nodes”.
U.S. Pat. No. 5,524,205 discloses a method of making protected changes to data stored in memory blocks in a database. The database described there is implemented on a hard disk and contains data about the state of a node in a data processing system, which are updated in the form of so-called transactions. A “transaction” corresponds to a group of changes made to change at least one node of the system from one state to the next. The database and two buffers (“undo buffer” and “redo buffer”) form a database system which is to ensure that the system can be restarted from a defined state if disturbances should occur during a transaction. To accomplish this, the database system performs a recovery in which prior to the beginning of the transaction, data about the latest state of the node are written into one of the buffers (“undo buffer”), and in which during the transaction, data about the next state of the node are written into the other buffer (“redo buffer”). If the transaction was not disturbed, the data stored in the redo buffer describe the current state of the node. If the transaction was disturbed, the data stored in the undo buffer describe the current state from which the system can be restarted. In the method and system described in U.S. Pat. No. 5,524,205, read/write accesses to two buffers are necessary, which signifies complex and slow memory management.
An article by S. Colombo et al, “Technologie der SDH-Netzelemente: die Software-Plattform”, Elektrisches Nachrichtenwesen, a journal published by the applicant, 4th Quarter 1993, pages 321-327, describes the use of object-oriented databases in network elements of an SDH communications network and addresses the subjects of memory management and persistency. A method or apparatus for making protected changes to the stored data is not described. A general description of SDH network elements and their management can be found in the same journal, on pages 329-337, in an article by M. P. Bosse et al, “Management von SDH-Netzelementen: eine Anwendung der Informationsmodellierung”.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for making protected changes to data stored in a database as well as a database system whereby fast memory management can be provided in a simple manner. In addition, a network element for a digital communications network with such a database system is to be provided.
The object is attained by a method with the features according to claim
1
and by a database system and a network element with the features according to the respective independent claims.
Accordingly, a method is proposed which comprises searching for a free memory block in the database for the new data, temporarily storing the number of this memory block in a nonvolatile semiconductor memory, and checking whether the writing of the new data into the free memory block was disturbed and, if so, continuing to manage the free memory block as such.
In this manner, new data which are to replace old data are written only into free memory blocks, so that no old data are overwritten. Thus, in the event of a disturbance or failure, the old data are completely available for restoring the system. To change the data, the database is controlled by a control unit which accesses the nonvolatile semiconductor memory, where it temporarily stores and manages the block numbers of the memory blocks to be written to, so that in the event of a disturbance or failure, all block numbers specifying the memory blocks involved in the change to the data will be available. Through the use of a semiconductor memory, the management of the database is significantly accelerated.
Further advantages are apparent from the subclaims.
It is particularly advantageously if, in connection with a transaction, only the block numbers of the first memory block of a memory area, the number of memory blocks, and the transaction number are temporarily stored in the nonvolatile semiconductor memory. In this manner, sufficient information for unambiguously identifying the memory blocks affected by the transaction, i.e., for identifying the respective block-number range, is stored. In the event of a disturbance or failure, the transaction can be undone at any time. Only little storage space is needed.
The invention can be used to advantage in a network element which is employed as a crossconnect, an add-drop multiplexer, or a line multiplexer for an SDH communications network.
REFERENCES:
patent: 5659744 (1997-08-01), Herbert
patent: 5666511 (1997-09-01), Suganuma et al.
patent: 5696933 (1997-12-01), Itoh et al.
patent: 5787460 (1998-07-01), Yashiro et al.
patent: 5954822 (1999-09-01), Yashiro et al.
Rietzke Arno
Sembach Frank
Alcatel
Lane Jack A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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