JPS6022782B2 - Initiated high-speed duplicate data control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an efficient control method for duplicate data in a distributed database system.

Today, with the development of information processing technology, distributed database systems are being discussed.

One of these is a method for controlling duplicate data. Duplicate data refers to data that is managed by physically different computers, but whose contents are the same.

The basic principle of the duplicate data control formula is that when one piece of data is updated, other duplicate data is also updated to maintain the identity of the duplicate data. The problem with maintaining identity is that
Each computer that manages duplicate data performs processing independently and in parallel, and the challenge is how to keep the content of the duplicate data managed by these computers the same.

To simplify the explanation, an example in which identity collapses will be explained using FIG. 1. In FIG. 1, there are a computer 1 and a computer 2 that have duplicate data.

Also, record R is one of the duplicate data. Now, suppose that an update request is made in the computer 2 to set the content of record R to be a, and a data update request is issued to the computer 2 to set the content of record R to b. Each computer executes these update requests. At this point, record R in computer 1 is a, and record R in computer 2 is b. Each computer notifies other computers of these update requests.
Each computer receives these notifications with some time delay and updates the duplicate data. That is, the computer 1 updates the code R to b, and the computer 2 updates the code R to a. In the example of FIG. 1, even if a similar update is performed, the contents of the vehicle duplication data managed by each convenience store will easily collapse. This is because the update order differs depending on each computer.

A subordinate majority voting method has been proposed as a method for maintaining identity, but it is difficult to put it into practical use because it takes too long to decide whether updates are allowed.

An object of the present invention is to provide a control method for multiple data that can determine update permission in a short time.

First, the principle of the present invention will be explained. If the data group updated at a certain timing is the same data group in each computer, identity can be easily maintained.

The present invention introduces the concept of logical time to this timing. Logical time is a logical time that is not physically the same in each computer but is logically synchronized.
The method for advancing the logical time will be explained below. After confirming that the logical times of all computers other than the privileged computer are the same as the privileged computer's logical time, the privileged computer advances the logical time of the privileged computer by one and sets the logical time of the computer outside of the privileged computer's view. Notify the time change order. When a computer other than the privileged computer receives an instruction to change the logical time from the privileged computer, it advances its own logical time by one and notifies the outside of the privileged computer of completion notification. The first embodiment of the present invention defines a method for advancing logical time outside a privileged computer, and includes a function to count logical time change completion notifications supplied from a computer other than a privileged computer, and a function to count logical time change completion notifications provided from a computer other than a privileged computer. A function to determine whether the number matches the number of computers other than the privileged computer, a function to advance the logical time of the privileged computer by one based on this determination, and a function to issue an instruction to change the logical time of the computer other than the privileged computer. This method is characterized by having the following functions. In this method, the logical time of the computer other than the privileged computer is equal to or one logical time earlier than the logical time of the privileged computer, so the notification of completion of logical time change supplied from the computer other than the privileged computer is counted. You can confirm that all computers have the same logical time simply by doing this. As a result, high-speed processing became possible. Next, the flow of data in the present invention will be explained using FIG. 2.

In order to simplify the explanation, the case of 3 computers will be explained. A certain computer (hereinafter referred to as A)
Assume that an update request occurs when the logical time of A is k. A notifies the privileged computer (hereinafter referred to as B) that an update request has occurred. Let this event be a.
When B receives a, it notifies a computer other than the privileged computer (hereinafter referred to as C) that a has occurred. Let this event be b. C stores the update request until C's logical time reaches k+N, and C stores the update request until C's logical time reaches k+N.
When it reaches N, the update request is executed.

Let this event be c. From the first example of the invention, it can be proven that event b ends before event c.

If update requests are executed according to the above procedure, the update requests executed at a logical time outside each conference will be the same, and it is possible to make the update order the same in each computer. In the second embodiment of the present invention, an update request generated from each computer at the logical time k of that computer is stored in the computer until the logical time k+N of the computer, and updated when the logical time reaches k+N. It shows the functions that execute
In addition to the first embodiment, a buffer for stacking update requests from N logical times ago to the present, a function for stacking update requests for duplicate data in the buffer, and a function for stacking update requests for the buffer when changing the logical time are provided. This method is characterized by having a function of executing only update requests issued N logical times ago.

Note that N is an integer of 2 or more, and the smaller the number, the more efficient the objective achievement is. The third embodiment of the present invention is for preventing unnecessary network 10, and in addition to the second embodiment, it has a function of preventing updating of the logical time when there is no update request in the buffer. This method is characterized by having the following.

Next, details of the present invention will be explained using the block diagram of FIG.

First, a first example will be described. In FIG. 3, the counter management device 1 is supplied with a logical time change completion notification from a computer other than the privileged computer through the terminal 2, advances the contents of the logical time counter 3 by one, and notifies the logical time management device 4 of the change. . The logical time counter 3 is a counter that counts logical time change completion notifications of computers other than privileged computers. The logic time management device 4 is activated by the counter management device 1 when the counter 3 is changed, and checks whether the value of the counter 3 matches the number of computers other than privileged computers, and when the values become the same. The privileged computer advances the logical time by one, and requests a change command through the terminal 5 to the non-privileged computer to advance the logical time. According to the first embodiment, the logical time of computers other than the privileged computer can be logically synchronized with the logical time of the privileged computer at high speed.

The second embodiment has the following functions in addition to the first embodiment.

The logical time management device 4 activates the data update device 6 when changing the logical time.

The command management device 7 is supplied with all update requests for duplicate data through a terminal 8 and records them in a buffer 9 together with their logical time. The data update device 6 is activated by the logical time management device 4 and executes the update request issued at the logical time of the computer minus N from among the update requests stored in the buffer 9. According to the second embodiment, the data group updated at each logical time becomes the same data group in each computer processing the data independently.

The third embodiment has the following functions in addition to the second embodiment.

The logical time management device 4 uses the buffer 9 when changing the logical time.
Refer to , and stop changing the logical time when there is no update request in the buffer. According to the third embodiment, the number of networks 10 can be reduced by preventing the logical time from advancing when unnecessary.

Next, details of the logical time management device 4 will be explained using FIG. 3. Logical time management device 4 coincidence circuit 41 and update decision circuit 4
Consists of 2.

The matching circuit 41 is activated by the counter management device 1 and determines whether the value of the counter 3 matches the number of computers other than privileged computers. When they match, the change determining circuit 4
Start 2. The change determination circuit 42 checks the contents of the buffer 9, and if there is even one update request, determines the progression of the logical time, advances the logical time of the computer by one, and activates the data update device 6. It also requests a logical time change command through the terminal 5 to computers other than the privileged computer to advance the logical time. Next, details of the data updating device 6 will be explained using FIG. 3.

The data update device 6 includes a subtracter 61, a counter 62, a coincidence circuit 63, and a gate circuit 64.

The subtracter 42 is activated by the logical time management device 4, subtracts N from the logical time value of the computer, and sets the result in the counter 62. The matching circuit 63 checks the logical time in the buffer 9 and the value in the counter 62, and when they match, notifies the gate circuit 64 that there is a match. The gate circuit 64 notifies the computer main body of the contents of the update request in accordance with the notification from the coincidence circuit 63. According to the present invention, the data group updated at each logical time becomes the same data group in each out-of-conview unit that is processed independently and in parallel.

This makes it possible to maintain consistency in the same way as standalone. Note that in the embodiments, in order to simplify the explanation, the present invention has been explained as a device independent of a computer, but the present invention can also be built into a computer.
Further, it is also possible to implement it by software, and these do not define the scope of the claims of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example in which identity collapses, FIG. 2 is an explanatory diagram showing the flow of data in the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a counter management device, 2 is an input terminal, and 3 is a counter management device.
is a logical time counter, 4 is a logical time management device, 5 is an output terminal, 6 is a data update device, 7 is a command management device, 8
9 represents an input terminal, 9 represents a buffer, 41 represents a matching circuit, 42 represents a change determining circuit, 61 represents a subtracter, 62 represents a counter, 63 represents a matching circuit, and 64 represents a gate circuit. O diagram O 2 diagram Sai 3 diagram

Claims (1)

[Scope of Claims] 1. Each computer in a distributed database system having duplicate data has a logical time, and one privileged computer among them receives a count signal when receiving a notification of completion of changing the logical time supplied from the privileged computer. a counter that receives the count signal and increments its contents by one, and determines whether or not this count value matches the number of computers other than the privileged computer, and based on this determination, the logic of the privileged computer is determined. A redundant data control method characterized by comprising a logical time management device that advances the time by one and issues a logical time change command to a computer other than a privileged computer. 2. Each computer in a distributed database system with duplicate data has a logical time, and one privileged computer among these computers outputs a count signal upon receiving a notification of completion of changing the logical time supplied from a computer other than the privileged computer. A counter management device, a counter that receives the count signal and increments its contents by one, determines whether or not this count value matches the number of computers other than the privileged computer, and based on this determination, the logical time of the privileged computer is set to 1. a logical time management device that issues a command to change the logical time to computers other than the privileged computer when the logical time advances; a buffer that stacks update requests for duplicate data from N logical times ago to the present; and a data update device that executes only update requests issued N logical times ago among update requests. 3. Each computer in a distributed database system with duplicate data has a logical time, and one privileged computer among these computers outputs a count signal upon receiving a notification of completion of changing the logical time supplied from a computer other than the privileged computer. A counter management device, a counter that receives the count signal and increments its contents by one, determines whether or not this count value matches the number of computers other than the privileged computer, and based on this determination, the logical time of the privileged computer is set to 1. A logical time management device that issues a logical time change command to computers other than the privileged computer, a buffer that stacks update requests for duplicate data from N logical times ago to the present, and a buffer that stacks update requests for duplicate data when the logical time changes. Duplication characterized by having a data update device that executes only update requests issued N logical times ago among update requests in a buffer, and means for preventing updating of the logical time when there is no data in the buffer. Data control method.