Abstract:
According to the present invention, a file recovery system is provided in which the commands for recovering files such as a historical file are unnecessitated and the recovery system configuration is independent of the host processing system. That is, since the equipment for achieving a file recovery does not have information about the location of the recovery data, information about the content of a file to be recovered is transmitted to a transmission line. The other equipments asynchronously receive the information and judges whether or not a file containing the same content exists in the own system. If its file exists, the content of the file is transmitted to the transmission line. The equipment achieving the file recovery asynchronously receives from the transmission line the file data of files such as a historical file and establishes data consistency by use of the buffered current data and the event number, thereby recovering files such as a historical file.

Description:
This application is a Continuation of application Ser. No. 06/924,789, filed Oct. 30, 1986 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a file recovery for a recovery system of files such as a historical file distributed to plurality of equipments connected to a common signal transmission line, and in particular, to a method and apparatus for distributed file recovery suitable for a system in which a file may possibly be destroyed and location of file recovery data cannot be determined. 
     In the conventional file system, although a plurality of files are distributed as described in a manual of a large-sized computer, the processing between files is controlled by a host computer in a concentrated fashion, and hence a command error may occur during a file recovery and the contents of a file thus recovered become different from the expected correct data; moreover, during the file recovery, the processing other than the recovery processing is prevented from being executed, which leads to a disadvantage that the processing efficiency of the system as a whole is lowered. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method of distributed file recovery which is capable of effecting a file recovery even if the location of the file recovery data of a historical file or the like is not known and which is capable of simultaneously accomplishing operations of other equipments while executing the historical file recovery. To this end, according to the present invention, there is provided a method of distributed file recovery in a distributed file system comprising a plurality of equipment connected to a common signal transmission path a plurality of files each containing data of the same content stored in a sequence characterized in that an equipment for achieving a file recovery transmits to a transmission path a file information having contents for the file recovery and each equipment having received the file information judges whether or not its own file includes data of the same contents, and if the data is included, the equipment transmits the data to the transmission path; equipment for effecting a file recovery judges a current data necessary for the recovery and receives the necessary current data from the transmission path and each data format is provided with an information required, when generating a recovery data from the current data and the transmitted data, to keep a data consistency with respect to the other files; and the equipment executes the file recovery based on the information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a schematic diagram illustrating an example of the overall configuration of a system having a loop transmission system and n equipments connected thereto; 
     FIG. 2 is a schematic block diagram of an equipment which may be used in the system according to the present invention; 
     FIG. 3 is a configuration diagram illustrating the format of data on a transmission line; 
     FIG. 4 is a configuration format illustrating the format of an input data to a receive buffer  206 ; 
     FIG. 5 is a configuration diagram of an input processing information memory unit according to the present invention; 
     FIG. 6 is a configuration diagram of an output processing information memory unit according to the present invention; 
     FIG. 7 is a flowchart demonstrating an operation flow of the information memory unit control according to the present invention; 
     FIG. 8 is a flowchart illustrating an operation flow of the file start judgment according to the present invention; 
     FIG. 9 is a flowchart illustrating an operation flow of the mutual supporting recover according to the present invention; 
     FIG. 10 is a schematic diagram showing the format of the historical data and the current data; 
     FIG. 11 is a flowchart showing an operation flow of the current data buffering of the present invention; 
     FIG. 12 is a schematic diagram illustrating the data format of the file start information according to the present invention; and 
     FIG. 13 is a flowchart showing an operation flow of the mutual supporter according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Description will be given of an embodiment of the present invention with reference to the accompanying drawings. 
     FIG. 1 is a schematic diagram showing the overall configuration of the present invention. 
     A loop transmission system of FIG. 1 comprises a one directional transmission loop  1  forming a common signal transmission path or line to which n equipments  11 ,  12 , . . . ,  1 n are connected. 
     FIG. 2 is a schematic diagram illustrating the configuration of an i-th equipment  1   i . The equipment li comprises an external memory  200  and processes, by use of an information processing system  204 , data received via a transmission control equipment  201  and a transmission line  1 , and then the data is stored in the external memory  200 . Data stored in the external memory  200  may also be accessed and processed by the information processing system  204 , and thereafter the result is transmitted via the transmission control equipment  201  to the transmission line  1 . 
     Next, description will be given of the transmission control equipment  201  and the information processing system  204  in this sequence. 
     First, the transmission control equipment  201  comprises a transmission process unit  202  and a transmission memory unit  203 . FIG. 3 is a schematic diagram illustrating the format of data received by the transmission control equipment  201  via the transmission line  1 . This format includes a flag  301  indicating the beginning or the end of the transmission line data, a content code  302  assigned corresponding to the content of data, an address field  303  indicating an address of an equipment that has transmitted the data, a data length field  304  containing the data length, a data field  305  containing the data, and a frame check sequence field  306  containing a frame check sequence for checking a transmission error. 
     When the transmission process unit  202 , for which a content code corresponding to the data to be received by the equipment  1   i  is registered in the transmission memory unit  203 , receives data from the transmission line  1 , the transmission process unit  202  checks the content code  302  of the transmission line data and determines whether or not the same content code has been registered in the transmission memory unit  203 . If this is the case, the data is transmitted to the information processing system  204 ; otherwise, the received transmission line data is transferred to the linked transmission line  1 . FIG. 4 is a schematic diagram illustrating the format of data passed from the transmission process unit  202  to the information processing system  204 . The format comprises a content code  401 , a source address of data transmission  402 , a data length  403 , and data  404 . 
     Next, the information processing system  204  will be described. 
     The information processing system  204  includes a transmission buffer  205  and a receive buffer  206  for storing the transmitted and received data, respectively, a processing unit  207  for temporarily processing information, an information memory unit  208  for storing information about the data to be processed by the processing unit  207 , a timer  209 , an external memory control unit  210  for controlling the data communication with respect to the external memory  200 , and a buffer  218  for the current data. The processing unit  207  is further divided into processing sections including an information memory control  211 , a file start judgment  212 , a mutual supporting recoverer  213 , a current data buffering  214 , a mutual supporter  215 , a file retriever  216 , and a file editor  217 . The mutual supporter  215 , the file retriever  216 , and the file editor  217  are processing sections collectively called a file module. Since each processing section operates in a data driven manner with reference to the information memory unit  208 , the information memory unit  208  will be first described prior to explanation of the processing unit  207 . The information memory unit  208  comprises an input processing information memory unit  501  (FIG. 5) and an output processing information unit  611  (FIG.  6 ). The input processing information memory unit  501  includes processing data information areas, namely, cells  511 - 517  corresponding to the processing sections  211 - 217 , respectively. Each cell of the cells  511 - 517  further comprises an input content code area  502  for indicating a content code of input data input to the processing section, a check flag area  503  for indicating the presence/absence of the input data, an input data output area  504 , an output content code area  505  for indicating a content code of an output data from the processing section, and a restrain flag  506  for indicating whether or not a processing section can be started. The above-mentioned content code is a code that is assigned in accordance with the meaning of the data to be set in the field  505 . The output processing information memory unit  611  includes processing data information areas, namely, cells  601 - 607  corresponding to the processing sections  211 - 217 , respectively as shown in FIG.  6 . Each cell of the cells  601 - 607  comprises an output content code area  608  for indicating a content code of output data, a data length area  609 , and an output data area  610 . 
     As for the operation of the processing unit  207 , the processing sections thereof may be activated in an arbitrary order; however, in this description, the processing sections are assumed to be activated in the order of the information memory unit control  211 , the file start judgment  212 , the mutual supporting recoverer  213 , the current data buffering  214 , the mutual supporter  215 , the file retriever  216 , and the file editor  217 . First, when the information memory unit control  211  is operated (the flowchart shown in FIG.  7 ), it is checked whether or not the receive buffer  206  contains data. If there exists data in the receive buffer  206 , a data item having the format of FIG. 4 is set in the information memory unit  208 . More specifically, the content code registered in the input content code area  502  is checked against the content code of the data in the receive buffer  206 . For any data for which the content code matches, data items (the transmission source address  402 , the data length  403 , and the data  404 ) are set in the input data area  504  and “1” is stored in the check flag area  503 . If data is missing in the receive buffer, the information memory unit control  211  does not take any action. Next, the file start judgment  212  starts its operation (flow-chart shown in FIG.  8 ). The file start information contains as the data thereof a content code corresponding to the data stored as a file in the external memory  200 . The file start information is set in the input processing information memory unit  501  during the initial processing at the startup of the equipment  1   i ; alternatively, based on the data received from the transmission line  1 , the information memory unit control  211  sets the file start information in the input processing information memory unit  501 . If the file start information is found to be missing as a result of the file start information presence/absence check, no action is taken; otherwise, the restrain flag  506  is set for “1” for the mutual supporter  215 , the file retriever  216 , and the file editor  217 , thereby restraining the execution of these three processing sections until the file recovery is completed. The file start judgment  212  sets the data containing the file start information as its substantial data in the output processing information memory unit  611 . The file start information code is set in the output content code area  608 . The processing of the file start judgment  212  has been described. Next, the mutual supporting recoverer  213  is activated (the flowchart shown in FIG.  9 ). In the input content code area  502  of the cell  512  in the input processing information memory unit  501  corresponding to the mutual supporting recoverer  213 , the content code associated with the contents of the chronological change file to be recovered and the content code of the file start information are registered in advance. 
     When the mutual supporting recoverer  213  is activated, the check flag area  503  is judged to determine whether or not all data registered in the cell  512  are present. If all data are present, the latest chronological change file data is edited by the use of the chronological change file data stored in the data area  504  of the cell  512  and the current data in the current data buffer  218 , and then the resultant data is stored in the external memory  200  via the external memory control unit  210 . The current data buffer  218  is then cleared and the restrain flag  506  is released for the mutual supporter  215 , file retriever  216 , and the file editor  217  to be described later, thereby completing the processing of the mutual supporting recoverer  213 . Moreover, the chronological change data is edited as follows. First, the buffered current data is checked against the chronological change data to determine the new and old data. As shown in FIG. 10, the format of the current data and the chronological change data includes a content code field  1001 , a data length field  1002 , and a data field  1003 . The data field  1003  is further divided into an event number field  1004  and a data field  1005 . The event number includes a data transmission source address  1006  and a sequence number assigned by the data transmission source. The event number added to the chronological change data is made to be identical with the event number of the latest current data used to generate the chronological change data; consequently, by comparing the event numbers, the chronological change data can be determined whether or not to be older than the buffered current data. As a result, the current data generated after the chronological change data generation can be identified, and hence by editing the chronological change data by sequentially using the current data, the latest chronological change file data can be edited. If all data registered to the cell  512  are not present when the mutual supporting recoverer  213  is activated, a timer judgment is executed. That is, in a case of a timeout, it is assumed that the file recovery data is missing in the system and the restrain flag  506  is released for the mutual supporter  215 , the file retriever  216 , and the file editor  217 , thereby completing the mutual supporting recoverer processing. If the timeout has not occurred, no special processing is accomplished, thereby completing the mutual supporting recovery processing. 
     Next, the current data buffering  214  is activated (the flowchart shown in FIG.  11 ). To the input content code area  502  of the cell  513  in the input processing information memory unit  501  corresponding to the current data buffering  214 , the content code of the current data used to edit the file is registered in advance. When the current data buffering  214  is activated, the check flag  503  of the pertinent cell  513  is checked to determine whether or not the current data has been set. If the current data has been set with the check flag=“1”, the current data stored in the data buffer  504  of the cell  513  is buffered into the current data buffer  218 . The check flag area  503  of the cell  512  is then cleared to “”, thereby completing the buffering processing. If the current data has not been set, no special processing is executed, thereby completing the buffering processing. 
     Next, the mutual supporter  215  is activated (the flowchart shown in FIG.  13 ). The mutual supporter  215  is activated when the file start information of FIG. 12 is present. That is, if the content code  1201  of the file start information has been registered to the input content code area  502  of the own cell  514  and the check flag  503  of the area corresponding to the file start information is “1”, the data corresponding to the data division  1204  of the file start information is fetched from the input data area  504  for the processing. In the concrete processing, based on the data associated with the data  1203  of the file start information, the content code of the file to be recovered is checked to determine whether or not it matches with the content code of the file in the equipment thereof. The content code of the file in the equipment is beforehand registered to the output content code area  505  of the cell  514  in the input processing information memory unit  501 . If the content codes match as a result of the check, the content of the file is read via the external memory control unit  210  and is set to the output data area  610  of the cell  604  in the output processing information memory unit  611 , the output content code is set to the content code area  608 , and the check flag  503  of the own cell  514  in the input processing information memory unit is cleared to “”, thereby completing the mutual supporting processing. If the content codes do not match as a result of the code check, the check flag  503  of the own cell  514  in the input processing information memory unit  501  is cleared to “”, thereby completing the processing of the mutual supporting recoverer  213 . 
     Next, the file retriever  216  and the file editor  217  are activated in this order. The file retriever  216  and the file editor  217  are executed if the areas registered to the check flag areas  503  of the pertinent cells  515 - 516  in the input processing information memory unit  501  have been set to “1”. More concretely, the file retriever  216  activates the external memory control unit  210 , reads the content of the file, writes the obtained data in the output data area  610  of the cell  605  in the output processing information memory unit  611 , and clears the check flag  503  of the cell  515  to “”. The file editor  217  fetches data from the input data area  504  of the cell  516 , performs editing of the data, writes the resultant data in the external memory  200 , and clears the check flag  503  of the cell  516  to “”, thereby completing the editing processing. However, if the restrain flag  506  of the cell  516  is “1”, the write operation on the external memory  200  is not achieved. In the file retriever  216  and the file editor  217 , if the areas registered to the check flag  503  are other than “1”, no special processing is accomplished, thereby completing the file retriever and file editor processing. 
     Next, the information memory unit control  211  is activated so as to repeat the processing described above. As described above, by periodically activating the information memory unit control  211 , the file start judgment  212 , the mutual supporting recoverer  213 , the current data buffering  214 , the mutual supporter  215 , the file retriever  216 , and the file editor  217 , each equipment can autonomously effect a recovery without necessitating information about the location where data for the chronological change file recovery exists in the system; moreover, the file editing can be achieved even during the chronological change file recovery. 
     Although the present invention has been described with reference to an embodiment of the chronological change file recovery method, it is not restricted by the embodiment, namely, the present invention is applicable to a case in general where the file configuration is determined according to the same idea and the data is edited according to the file configuration. 
     Although the embodiment includes a loop configuration as a common signal transmission line, the present invention can be widely applied to any common transmission lines of the bus type, star type, and network type; moreover, lines or paths of the radio transmission and the common transmission type (for the wire and radio transmission). 
     According to the present invention, for a file recovery of a chronological change file or the like, the location of the recovery data need not be known, and hence even if there exists an equipment which is executing a file recovery in the system, the other equipments need not change the operation mode, which facilitates the control. In an equipment which is executing a file recovery, file editing can also be achieved on current data concurrently with the file recovery, which leads to an effect that the file recovery is effected at a high speed.