JPH01239650A - Journal acquiring system - Google Patents

Abstract

PURPOSE:To improve the performance of an on-line system by outputting the content of a journal buffer to a spare external memory device when a fault is generated. CONSTITUTION:Records (1-10) as history information are buffered in the journal buffer 31, and a CPU issues the output request of the records (1-5), and the records (1-5) are buffered in the buffer 51 of a magnetic tape device, however, figure shows a case where the records (1-3) are outputted to the tape 52 actually. In such a case, a pointer PB indicates the record 5, and a pointer PR indicates the record 3. The CPU issues the output request of the records to the record 5 in the journal buffer 31, and since the records (1-3) are already outputted to the tape 52, the storage areas of the records (1-3) in the buffer 31 can be used again, and since no output request of the records (6-10) is issued, the CPU issues the output request to the tape device successively. In such a way, it is possible to improve the performance of the on-line system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a journal acquisition method for an online system, and when an external storage device such as a magnetic tape device with a buffering function is used as a journal file, the external storage The present invention relates to a journal acquisition method suitable for continuously outputting records to a spare external storage device when a failure occurs in a device.

[Conventional technology]

An online system is equipped with an external storage device such as a magnetic tape device as a journal file, and acquires history information of online processing as a journal in the external storage device.
When the system goes down, the system is intended to be restored to the state immediately before the system went down based on the contents of the external storage device. Conventionally, the method for speedily acquiring this type of journal is to prepare a journal buffer in the central processing unit (CPU), buffer history information in the journal buffer, and store the contents in external storage when the buffer is full. There is a method for outputting to a device. In addition, as a publicly known document related to this, for example, Japanese Patent Application Laid-Open No. 58-223856 can be mentioned.

[Problem to be solved by the invention]

One way to further speed up journal acquisition is to use an external storage device with a buffering function, such as a magnetic tape device, to transfer records buffer-to-buffer between the CPU's journal buffer and the external storage device's buffer. A possible method is to transfer the data and output it from a buffer to a recording medium such as a magnetic tape at any time. However, if the external storage device used as a journal file fails and the CPU continues journal output using a spare external storage device that also has a buffering function, the
The PU does not know how far the contents of the buffer have been written to the storage medium by the failed external storage device, and it is necessary to re-output the records to the spare external storage device starting from the first record of the journal buffer, which may affect the operation and performance of the online system. There is a problem above.

The purpose of the present invention is to provide a backup buffering function to the external storage device used as a journal file, without re-outputting records from the beginning of the journal buffer. The object of the present invention is to provide a journal acquisition method that allows continuous output to an external storage device.

[Means to solve the problem]

The above purpose is to manage, in the central processing unit, a first pointer indicating the record number of the journal buffer output to the external storage device and a second pointer indicating the record number written by the external storage device to the recording medium. , when a failure occurs in an external storage device with a buffering function that is being used as a journal file, the central processing unit outputs the contents of the journal buffer to a spare external storage device based on the pointer. .

[For production]

The central processing unit buffers records indicating processing history in a journal buffer, issues an output request, and outputs the contents of the journal buffer to an external storage device. Then, the first pointer is updated. The external storage device once buffers the output records from the central processing unit, sequentially writes them to a recording medium, and notifies the central processing unit of the record number. In response to this, the central processing unit
Update pointer.

When detecting a failure in the external storage device in use, the central processing unit outputs records after the record number indicated by the second pointer from the journal buffer to the spare external storage device. In other words, if the external storage device in use breaks down,
The central processing unit does not have to start over from the first record of the journal buffer.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of an embodiment of an online system to which the present invention is applied. Messages sent from the terminal 1o are sent to the central processing unit (CPU) via the communication control device 2o.
) passed to 30. CI) The U 30 determines and starts a user application program (UAP) 34 that performs business processing based on the received message. When the UAP 34 executes business processing and requests the CPU 30 to update the database 40, the CPU 30 updates the database 4o and simultaneously buffers the update history information in the journal buffer 31. On the other hand, the magnetic tape device 50 has a buffering function, and when the CPU 30 issues an output request, the contents of the journal buffer 31 are transferred to the buffer of the magnetic tape device 5o at high speed in a buffer-to-buffer format. . The magnetic tape device 5o is a CPU
Independently of the processing in step 30, the contents of the own buffer are output to the magnetic tape. Note that 50' is a spare magnetic tape device.

The pointer (PB) 32 in the CI'') U30 indicates the last record number transferred from the journal buffer 31 to the buffer of the magnetic tape device 5o, and the pointer (PR)
33 indicates the last record number output from the own buffer to the magnetic tape by the magnetic tape device 5o. The CPU 30 uses the pointer 32 every time it issues an output request to the magnetic tape device 50.
Update.

On the other hand, the magnetic tape device 50 notifies the CPU 30 of the record number of the record output from its own buffer to the magnetic tape. In response to this, the CPU 30 updates the pointer 33.

Hereinafter, the operation when a failure occurs in the magnetic tape device 50 being used as a journal file will be explained using a specific example.

FIG. 2 shows the relationship between the journal buffer 31 of the CPU 30, the buffer 51 of the magnetic tape device 50, and the magnetic tape 52. In this example, the journal buffer 31
Records 1 to 10 as VW information are buffer-linked to CI) U 30 as records l, 2, 3, 4.5.
Request output to the buffer 51 of the magnetic tape device 50.
Records 1.2, 3, and 4.5 are buffered, but only records 1, 2.3 are actually output to the magnetic tape 52.

In this case, pointer (PB) 32 indicates record number 5, and pointer (PR) 32 indicates record number 3. The CPU 30 issues a request to output up to record 5 in the journal buffer 31, and records 1 to 3 of them have already been output to the magnetic tape 52, so the storage area for records 1 to 3 in the journal buffer 31 is available for use. It is. Furthermore, since no output request has been made for records 6 to 10, CI) U aO continues to issue an output request to the magnetic tape device 50.

FIG. 3 shows that when a failure occurs in the magnetic tape device 50 in the state shown in FIG.
This shows what happens to the records written to 2'. Note that the buffer of the spare magnetic tape device 50' is omitted in FIG.

When the CPU 30 detects a failure in the magnetic tape device 50 in use, it checks the pointer (PR) 32. In this example, since the pointer 32 indicates record number 3, U30 outputs record 4 and subsequent records in the journal buffer 31 to the spare magnetic tape device 50'. In the spare magnetic tape device 50'', the journal buffer 31
The record group after record 4 is buffered in its own buffer and sequentially written to the magnetic tape 52''.

In the embodiment, a magnetic tape device is used as the journal file, but it goes without saying that any external storage device other than the magnetic tape device may be used as long as it has a buffering function.

〔Effect of the invention〕

As explained above, according to the present invention, when a failure occurs in the external storage device in use, there is no need to re-enter the journal buffer from the beginning of the journal buffer, and the backup external storage device is Since the storage device can output records that have not yet been written, wasteful processing can be eliminated, the operation and performance of the online system can be improved, and journal acquisition for high-traffic online systems can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of an online system to which the present invention is applied, and FIGS. 2 and 3 are diagrams showing specific examples for explaining the operation of FIG. 1. 30...Central processing unit (CPU), 31...Journal buffer, 32.33...Pointer, 40...Database,
50.50'...Magnetic tape device, 51...Magnetic tape buffer, 52.52'...Magnetic tape.

Claims (1)

[Claims] (1) Provide a journal buffer in the central processing unit and use an external storage device with a buffering function,
The central processing unit outputs a record indicating a processing history to the external storage device via a journal buffer, and the external storage device once buffers the output record from the central processing unit and then writes it to a recording medium. In the journal acquisition method, the central processing unit manages a pointer indicating a record number output to the external storage device and a pointer indicating a record number written to a recording medium by the external storage device, A journal acquisition method characterized in that when a failure occurs in an external storage device, the central processing unit outputs the contents of the journal buffer to a spare external storage device based on the pointer.