JPH09152985A - Method and system for journal backup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently back up a journal by writing journal data even in a buffer in a computer system and transferring the journal data to the backup side of a remote computer system. SOLUTION: The journal data is stored in a transfer source external storage means 30 of the computer system 10 and its serial number is stored; and the journal data is stored even in the buffer 12 in the system and when the journal data is transferred to a journal storage means 50, the serial number corresponding to the journal data which is already transferred is stored. Here, when a transfer means 15 transfers the journal data to the remote computer system 40, the stored serial numbers are checked to decide journal data from a type number which is already transferred to the remote computer system 40 to a type number which is already written to the transfer source external storage means 30, and when there is no journal data in the buffer 12, data is read out of the transfer source external storage means 30 and transferred.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a journal backup method and system, and more particularly to a journal backup method and system for obtaining a journal backup between computer systems connected via a communication medium.

More specifically, the present invention relates to a journal backup method and system for obtaining a backup of a journal to be obtained for the purpose of recovery when an update transaction process occurs in a computer system.

[0003]

2. Description of the Related Art Conventionally, when performing update transaction processing on a database or the like, journal data is acquired from an external storage device that holds journal data generated at the time of update, for the purpose of recovery when a failure occurs. At this time, the external storage device may become full (FULL), or the journal may be lost due to a failure of the external storage device itself. In order to prevent such a failure, a method of reading the journal in the external storage device to obtain a backup of the journal data is used.

FIG. 11 shows an example of backing up a journal in a conventional external storage device. The computer system shown in the figure includes a backup device 10 and an external storage device 2.
0, 60, MT (magnetic tape) 30, F which is a portable medium
It is composed of a D40 and a remote computer 50. The external storage devices 20 and 60 are realized by magnetic disk devices, and the external storage device 20 stores journal data generated in the update transaction processing. The external storage device 60 stores the journal data transferred via the communication medium.

The backup device 10 shown in FIG. 1 reads a journal in the external storage device 20, stores it in the MT 30 or FD 40, or transfers the acquired journal data to a remote computer 50 connected via a communication medium. The remote computer 50 stores the transferred journal data in the external storage device 60 and backs up the journal.

[0006]

However, the backup device 10 reads the journal stored in the external storage device 20 for the purpose of recovery when a failure occurs in performing the update transaction processing for the above-mentioned database or the like. And transfer the journal to the remote computer system 50 connected via the communication medium,
The method of acquiring a backup has a problem that a large amount of time is required for I / O access when reading a journal from the external storage device 20.

The present invention has been made in view of the above points, and when performing an update transaction for a database or the like, a journal acquired for the purpose of recovery in the event of a failure can be efficiently backed up to a remote computer system. An object is to provide a journal backup method and system.

[0008]

According to the present invention, journal data, which is acquired for the purpose of recovery in the event of a failure when performing update transaction processing for information in a database or a storage medium in a computer system, is transmitted via a communication medium. In a journal backup method that acquires as a backup to a remote computer system connected by a remote computer system, when writing the journal data to an external storage device, the journal data is also written to the buffer in the computer system and the journal data in the buffer is written to the remote computer system. Transfer to the backup side to get a backup of journal data.

FIG. 1 is a diagram for explaining the principle of the present invention. According to the present invention, the buffer acquires journal data during update transaction processing (step 1), writes the journal data in the buffer to the transfer source external storage device, and stores the written serial number in the transfer source external storage device. In advance (step 2), the data is transferred from the buffer or the external storage device of the transfer source to the backup side, and the transferred serial number is stored (step 3), and the written serial number and the backup side are transferred. Of the serial numbers of the above, the journal data corresponding to the serial numbers after the transferred serial number and before the written serial number are acquired (step 4), and the acquired journal data is transferred to the backup side, The transferred serial number is stored (step 5), and the transferred journal data is stored in the storage means on the backup side (step 6).

In step 4 above, when the journal data is acquired, the serial number is transferred after the transferred serial number.
Only when the journal data corresponding to the serial number before the written serial number does not exist in the buffer, the journal data is acquired from the external storage device of the transfer source. In addition, a flag is added to the journal data in the buffer to distinguish whether it has been transferred or not, and the journal data that has not been transferred to the backup side is not erased based on the flag.

FIG. 2 is a diagram showing the principle of the present invention. The present invention relates to the database 20 in the computer system 10.
An update unit 13 for performing an update transaction process on information in a storage medium, a transfer unit 15 for transferring journal data acquired for the purpose of recovery in the event of a failure to a remote computer system 40 connected via a communication medium, In the journal backup system having the journal storage means 50 for storing the journal data transferred in the remote computer system 40, the buffer 12 for writing the journal data acquired by the updating means 13 and the computer system 10 are connected and updated. Transfer source external storage means 30 for writing the journal data acquired by the means 13, and the buffer 12
It has a journal acquisition means for acquiring the journal data therein and passing it to the transfer means 15.

The journal acquisition means stores the first serial number holding means 16 for holding the serial number in which the journal data is written in the transfer source external storage means 30 and the serial number of the transferred journal data in the journal storage means 50. A second serial number holding means 17 for holding and a first serial number holding means 16
And the serial number of the second serial number holding means 17 are compared, and the first serial number holding means 1 is provided after the serial number of the second serial number holding means 17.
The serial number selecting means 18 for selecting a serial number corresponding to the serial number before the serial number 6 and the journal data corresponding to the serial number acquired by the serial number selecting means 18 are acquired from the buffer 12 and stored in the buffer 12. It includes a journal selecting means 19 which is acquired from the transfer source external storage means 30 only when it does not exist in the storage unit 12.

Further, the present invention further comprises journal data erasure limiting means which does not erase the journal data stored in the buffer 12 before the transfer processing by the transfer means 15. Thus, the present invention stores journal data in the transfer source external storage means 30 of the computer system 10,
When the serial number of the stored journal data is stored, the journal data is also stored in the buffer 12 in the system, and the journal data is transferred to the journal storage means 50 of the remote computer system 40, the transferred journal is The serial number corresponding to the data is stored. Here, when the transfer means 15 transfers the journal data to the remote computer system 40, the stored serial number is checked and the remote computer system 40 is checked.
Then, the journal data after the transferred serial number and up to the serial number for which writing to the transfer source external storage means 30 has been completed is determined. As a result of the determination, if the journal data is in the buffer 12, the journal data is read from the buffer 12 and transferred. If the journal data does not exist in the buffer 12, the transfer source external storage means 30 Read and transfer.

At this time, the I / O access time is shortened if the journal data is not read from the transfer source external storage means 30 as much as possible, so the journal data stored in the buffer 12 is transferred to the remote computer system 40. It is desirable not to be erased until. Therefore, by managing with a flag for recognizing whether the data has been transferred to the remote computer system 40, the journal data is held in the buffer 12 until the data is transferred to the remote computer system 40, and the transfer source external storage means It becomes unnecessary to read the journal data from 30. Further, when it is recognized that the transfer has been completed, the journal data in the transferred buffer can be erased, so that the amount of data in the memory can be small.

Since I / O access to an external storage device connected to the computer system requires a great deal of processing time, storing journal data in a buffer in the computer system shortens the access time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the configuration of a journal backup system of the present invention. The system shown in the figure is a computer system 10 for performing update transaction processing, a database 20 connected to the computer system 10 and updated by an update transaction, an external storage medium 30 such as a magnetic disk, the computer system 10 and a communication medium 60. And a remote computer system 40 for backup of journals, and an external storage medium 50 for storing backups of journals connected to the remote computer system 40.

The computer system 10 is composed of an update transaction 11, a buffer 12, a data update unit 13, a journal file acquisition unit 14, a journal transmission unit 15, a written counter 16 and a transferred counter 17. The update transaction 11 runs on the computer system 10, and the data update unit 13 is executed by extension of the data update of the update transaction 11.

The data updating unit 13 updates the contents of the database 20 and transfers the journal data 121 to the buffer 12. At this time, the data updating unit 13
The buffer 12 is cyclically used to acquire the journal data 121. A serial number is uniquely assigned to each journal data 121.

Further, the journal file acquisition unit 14 of the computer system 10 writes the journal data to the external storage device 30 and manages the written counter 16 for managing the serial number of writing the journal data 121.
Register the serial number of the journal data written in.

The journal transmission unit 15 transfers the journal data acquired on the computer system 10 side to the remote computer system 40 side. Details will be described later with reference to the flowchart shown in FIG. The written counter 16 is a counter that manages the serial number of writing to the external storage medium 30 up to the serial number.

The transferred counter 17 is a counter for managing how many serial numbers the journal transmission unit 15 has completed transferring the journal data to the remote computer system 40 connected via the communication medium 60. The external storage medium 30 includes a journal file 3 in which journal data is stored by the journal file acquisition unit 14.
One.

The remote computer system 40 is equipped with a journal receiving unit 41 that receives journal data transferred from the journal transmitting unit 15 of the computer system 10 via the communication medium 60 and stores the journal data in the external storage device 50.
The external storage device 50 has a journal file 51 in which journal data is stored by the journal receiving unit 41.

FIG. 4 is a flow chart showing the operation of the journal transmission unit of the present invention. Step 101) First, the journal transmission unit 15 of the computer system 10 first determines the serial number of the written counter 16 that manages the serial number of the journal writing to the external storage device 30 and the serial number of the remote computer system 40. Up to the serial number of the transferred counter 17 for managing whether or not the journals have been transferred, the serial number not transferred to the remote computer system 40, that is, the serial number transferred to the remote computer system 40 side or later, and the computer system. External storage device 10
Sequential data up to the serial number that has been written to is determined. When the value of the written counter 16 is larger than the transferred counter 17 (remote computer system 4
If there is untransferred journal data on the 0 side), the process proceeds to step 102. If not, the process is ended assuming that the journal transfer is completed.

Step 102) If there is journal data up to the serial number that has not been transferred to the remote computer system 40, that is, the transferred serial number or later and the writing to the external storage device 30 of the computer system 10 has been completed,
It is determined whether this journal data exists in the buffer 12. If so, go to step 103,
If it does not exist, the process proceeds to step 104.

Step 103) If the journal data exists in the buffer 12, the journal data in the buffer 12 is transferred to the remote computer system 40, and the process proceeds to step 106. Step 104) If the journal data does not exist in the buffer 12, the untransferred journal data is read to the remote computer system 40 side from the journal file 31 written in the external storage device 30.

Step 105) Journal sending unit 15
Transfers the journal data read from the external storage device 30 to the remote computer system 40. Step 106) In the communication control unit (not shown) in the journal transmission unit 15, it is judged whether or not the transfer process of the journal data to the remote computer system 40 is correctly performed,
If it is not done correctly, try again.
The process proceeds to step 101.

Step 107) When the transfer processing is correctly performed in Step 106, the transfer counter 1
The serial number of the transferred journal data is registered in 7. As described above, the remote computer system 40 is stored in the buffer 12.
If there is journal data to be transferred to the remote computer system, the journal data is stored in the buffer 12 in the remote computer system 4.
By transferring the data to 0, it is possible to reduce the reading of the journal data from the journal file 31 of the external storage device 30, reduce the number of I / O accesses in the journal backup acquisition process, and improve the processing efficiency.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. [Example 1] FIGS. 5 and 6 are diagrams for explaining an example of a first operation of journal backup according to an embodiment of the present invention. FIG. 5 shows a state before the journal having the serial number “7” is transferred from the computer system 10 to the remote computer system 40. FIG. 6 shows that the journal having the serial number “7” is transferred to the remote computer system 40. The latter state is shown.

Now, as shown in FIG. 5, the computer system 1
In the buffer 12 of 0, the journal data “7”,
“8”, “9”, and “10” are stored as the data updated by the data updating unit 13. Then, the journal file acquisition unit 14 completes the writing of the journal data of the serial number “7” stored in the buffer 12 to “7” of the journal file 31 of the external storage device 30, and the serial number “7” is written. It is set in the counter. Further, at this time, the journal data stored in the journal file 51 of the external storage device 50 connected to the remote computer system 40 has already been transferred to the remote computer system 40, and the journal data are serial numbers “1”, “2”,
The data are "3", "4", "5", and "6".

A case will be described below in which the journal transmission unit 15 transfers untransferred journal data to the remote computer system 40 in the above-mentioned situation. The journal transmission unit 15 refers to the written counter 16, and the journal data currently stored in the journal file 31 of the external storage device 30 at the end is the serial number “7”.
Recognize that it is the data of.

Next, the journal transmission unit 15 refers to the transferred counter 17, and the journal data currently stored in the journal file 51 of the external storage device 50 of the remote computer system 40 at the last is the data with the serial number “6”. Recognize that. Here, comparing the serial number “7” of the written counter 16 and the serial number “6” of the transferred counter 17, the serial number of the written counter 16 is larger, so that the journal transmission unit 15 is set to the remote computer system 40 side. It is determined that there is journal data that has not been transferred yet.

As a result, the journal transmission unit 15
Reads the journal data of serial number "7" from the buffer 12 and transfers it to the remote computer system 40 side. Journal receiving unit 4 of remote computer system 40
1 writes the received journal data of the serial number “7” in the journal file 51 of the external storage device 50.

When the transfer of the journal data is completed, the serial number “7” is registered in the transferred counter 17 of the computer system 10. As a result, the contents of the transferred counter 17 and the external storage device 50 of the remote computer system 40 are updated as shown in FIG.

[Example 2] FIGS. 7 and 8 are diagrams for explaining a second example of the journal backup operation according to the embodiment of the present invention. FIG. 7 shows a state before the journal with serial number “7” is transferred from the computer system 10 to the remote computer system 40. FIG. 8 shows the journal with serial number “7” as the remote computer system 40.
Shows the state where the transfer is completed. In this example, the remote computer system 40 has an untransferred journal, and the buffer 12 has no journal to be transferred to the remote computer system 40 side.

The journal transmission unit 15 refers to the written counter 16 and recognizes that the journal data currently stored in the journal file 31 of the external storage device 30 is data up to the serial number “7”. Next, the journal transmitter 15 uses the transferred counter 1
7, the remote computer system 40 at the end now
It recognizes that the journal data stored in the journal file 51 of the external storage device 50 is data up to the serial number "6".

When comparing the value of the written counter 16 and the serial number of the transferred counter 17, the serial number of the written counter 16 is larger, so that the journal transmission unit 1
5 determines that there is journal data that has not been transferred yet on the remote computer system 40 side.

As a result, the journal transmission unit 15
Searches for untransferred journal data of serial number "7" in the buffer 12, but since it does not exist, it searches the journal file 31 of the external storage device 30 and reads the journal data of serial number "7". Transfer to the remote computer system 40 side.

The journal receiving unit 41 of the remote computer system 40 writes the received journal data of serial number “7” into the journal file 51 of the external storage device 50. As a result, the serial number “7” is registered in the transferred counter 17 of the computer system 10.

As a result, the contents of the transferred counter 17 and the external storage device 50 are updated as shown in FIG. Note that the examples shown in FIG. 7 and FIG. 8 are processing when there is no written serial number journal data in the buffer 12 of the computer system 10. The timing for clearing the buffer 12 and the external storage of the remote computer system 40 are shown. Depending on the difference in the timing of transfer to the device 50, the buffer 12
This is a process that occurs when journal data to be transferred is deleted.

Therefore, the number of times the external storage device 30 is accessed is significantly reduced as compared with the conventional technique. Further, in order to prevent the external storage device 30 from being accessed at all, a method of giving a flag indicating whether or not the journal data in the buffer 12 has been transferred may be considered. For example, it can be solved by setting a transferred flag (1 = transferred, 0 = untransferred) and setting it so as not to erase untransferred data as long as it exists in the buffer 12.

[Example 3] FIGS. 9 and 10 are diagrams for explaining a third example of the journal backup operation according to the embodiment of the present invention. FIG. 9 shows a state in which the journals with the journal serial numbers “2”, “3”, and “4” have not been transferred from the computer system 10 to the remote computer system 40 side, and FIG. 10 shows the journal serial numbers “2” and “3”. 4 shows the state after the journal data of "4" is transferred to the remote computer system 40 side. This example shows a case where there are only two journals “3” and “4” to be transferred to the remote computer system 40 side in the buffer 12.

The journal transmission unit 15 refers to the written counter 16 and the journal data currently stored in the journal file 31 of the external storage device 30 is serial number “1”, “2”, “3”, “4”. Recognize that this is journal data. Next, the journal transmitter 15 uses the transferred counter 1
7, it is recognized that the journal data having the serial number “1” has already been transferred to the external storage device 40 of the remote computer system 40.

When comparing the serial number of the written counter 16 and the serial number of the transferred counter 17, the serial number of the written counter 16 is larger, so the journal transmission unit 15 still transfers the serial number to the remote computer system 40 side. It is determined that there is journal data that has not been created. That is, it is recognized that there are three journal data items to be transferred, “2”, “3”, and “4”, according to the serial number of the written counter 16.

As a result, the journal transmission unit 15
First searches the buffer 12 for the journal data with the serial number “2”, but since it does not exist, it searches the journal file 31 in the external storage device 30 and reads the journal data with the serial number “2” to remote the journal file 31. Transfer to the computer system 40 side.

The journal receiving unit 41 of the remote computer system 40 writes the received journal data of serial number “2” into the journal file 51 of the external storage device 50. Next, the journal transmission unit 15 reads the journal data of the serial numbers “3” and “4” in the buffer 12, and therefore, the journal transmission unit 15 reads the journal data of the serial number and transfers the journal data to the remote computer system 40. . As a result, the journal receiving unit 41 writes the received journal data in the journal file 51 of the external storage device 50.

The last journal transmitter 15 stores the serial number “2” in the transferred counter 17 of the computer system 10.
Register "3" and "4". As a result, the contents of the transferred counter 17 and the external storage device 50 are updated as shown in FIG.

In this way, among the serial numbers registered in the written counter 16, only the journal data not registered in the buffer 12 is read from the external storage device 30 and transferred to the external storage device 50 of the remote computer system 40. By doing so, the number of times the external storage device 30 is accessed can be reduced.

That is, in the above embodiment (Example 3),
Conventionally, in order to acquire 3 journal data,
It was necessary to access the external storage device 30 of the transfer source three times, but by applying the present invention, only one access is required. It should be noted that the present invention is not limited to the above-described embodiments, and various applications within the scope of claims
Changes are possible.

[0049]

As described above, according to the journal backup method and system of the present invention, in the journal backup acquisition processing between the computer systems connected via the communication medium, the writing of the journal to the external storage device is performed. A counter that manages how many serial numbers have been completed, a counter A that manages how many journals have been transferred to the remote computer system by serial number, and a counter A that has serial numbers that have been transferred to the remote computer system A counter B that manages the serial number is provided, and the serial number of the counter A and the serial number of the counter B are checked, and writing to the external storage device on the computer system side is completed after the serial number that has been transferred to the remote computer system. Judge the journal data up to the serial number, and if there is the corresponding journal data in the buffer, Performs a process of transferring the journal data in § a remote computer system. Then, the journal data stored in the external storage device of the transfer source is transferred only when there is no untransferred journal data in the buffer. This reduces the number of I / O accesses to the external storage device on the computer system side,
The transfer processing efficiency of the journal to the remote computer system is improved, and the contents of the journal of the external storage device and the journal acquired by the remote computer system are substantially the same.

Therefore, even when the external storage device on the computer system side is full (FULL) or the journal disappears due to a failure, the remote computer system can hold a journal that substantially matches the external storage device.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a principle configuration diagram of the present invention.

FIG. 3 is a configuration diagram of a journal backup system of the present invention.

FIG. 4 is a flowchart showing the operation of the journal transmission unit of the present invention.

FIG. 5 is a diagram (No. 1) for explaining the first operation of the journal backup according to the embodiment of the present invention.

FIG. 6 is a diagram (No. 2) for explaining the first operation of the journal backup according to the embodiment of the present invention.

FIG. 7 is a diagram (No. 1) for explaining the second operation of the journal backup according to the embodiment of the present invention.

FIG. 8 is a diagram (No. 2) for explaining the second operation of the journal backup according to the embodiment of the present invention.

FIG. 9 is a diagram (No. 1) for explaining the third operation of the journal backup according to the embodiment of the present invention.

FIG. 10 is a diagram (No. 2) for explaining the third operation of the journal backup according to the embodiment of the present invention.

FIG. 11 is a diagram showing an example of backing up a journal in a conventional external storage device.

[Explanation of symbols]

 10 computer system 11 update transaction 12 buffer 13 data updating unit, data updating unit 14 journal file acquisition unit 15 journal sending unit, transfer unit 16 written counter, first serial number holding unit 17 transferred counter, second serial number holding unit 18 serial number selection means 19 journal selection means 20 database 30 external storage device, transfer source external storage means 31 journal file 40 remote computer system 41 journal receiver 50 external storage device, journal storage means 51 journal file 60 communication medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Akiba 223-1, Yamashita-cho, Naka-ku, Yokohama-shi, Kanagawa NTT Software Corporation

Claims (7)

[Claims] 1. A remote computer system connected via a communication medium with journal data, which is acquired for the purpose of recovery in the event of a failure when performing an update transaction process for information in a database or a storage medium in the computer system. In the journal backup method to obtain as a backup, when writing the journal data to an external storage device,
A journal backup method comprising: writing the journal data in a buffer in the computer system, transferring the journal data in the buffer to a backup side of the remote computer system, and obtaining a backup of the journal data. 2. A first step in which the buffer acquires the journal data during update transaction processing, and the journal data in the buffer is written to an external storage device of a transfer source, and the external storage device of the transfer source has been written. And a third step of storing the transferred serial number from the buffer or the external storage device of the transfer source to the backup side and storing the transferred serial number. A fourth step of comparing the completed serial number with the serial number transferred to the backup side, and acquiring journal data corresponding to the serial number after the transferred serial number and before the written serial number. Then, transfer the acquired journal data to the backup side,
The journal backup method according to claim 1, wherein a fifth step of storing the transferred serial number and a sixth step of storing the transferred journal data in the storage means on the backup side are performed. 3. The journal data corresponding to a serial number after the transferred serial number but before the written serial number does not exist in the buffer when the journal data is acquired in the fourth step. 3. The journal backup method according to claim 2, wherein the journal backup is acquired only from the external storage device of the transfer source. 4. The journal backup method according to claim 2, wherein the journal data in the buffer is provided with a flag for distinguishing whether it has been transferred or not, and the journal data that has not been transferred is not erased. 5. A remote computer system in which update means for performing update transaction processing on information in a database or a storage medium in a computer system and journal data to be acquired for the purpose of recovery in the event of a failure are connected via a communication medium. And a buffer for writing the journal data acquired by the updating means, in a journal backup system having a transfer means for transferring to the remote computer system and a journal storage means for storing the transferred journal data in the remote computer system; A transfer source external storage unit connected to the system for writing the journal data acquired by the updating unit, and a journal acquisition unit for acquiring the journal data in the buffer and passing the journal data to the transfer unit. Journal backup system to collect. 6. The journal acquisition means holds a first serial number holding means for holding a serial number in which the journal data is written in the transfer source external storage means, and a serial number for the transferred journal data in the journal storage means. Comparing the serial numbers of the second serial number holding means, the first serial number holding means, and the second serial number holding means, and holding the first serial number after the serial number of the second serial number holding means. A serial number selecting means for selecting a serial number corresponding to a serial number before the serial number of the means, and journal data corresponding to the serial number acquired by the serial number selecting means exists in the buffer, is acquired from the buffer, and the buffer 6. The journal backup system according to claim 5, further comprising a journal selecting unit that acquires from the transfer source external storage unit only when it does not exist. 7. The journal data erasure limiting means that does not erase the journal data stored in the buffer before the transfer processing by the transfer means.
Journal backup system described.