JPH04184641A - Data base restoring system - Google Patents

Abstract

PURPOSE:To reduce the consumption of a magnetic tape and at the same time to restore a data base at a high speed by reducing the quantity of data which are stored in an external store medium like the magnetic tape, etc., from an external temporary medium like a magnetic disk, etc., and furthermore reducing the quantity of data which are processed when the data base is restored from the external store medium. CONSTITUTION:When an operation is started, the initial state of an old data base 1 is saved to a data base saving tape 7. Thereafter the data on the updated part are successively generated and written into a disk file 3. When the file 3 is filled with the data, the data are called out of the file 3 by a journal collecting means 4 in the order opposite to the writing order and stored in a magnetic tape 5. Thus the quantity of data to be produced to the tape 5 is extremely reduced, and a file area is secured in a new data base 8 when a data base having a fault is restored with use of a produced journal. Then the faulty data base is restored from the tape 7 and the data on each file are read out by a restorage processing means 6 in the order opposite to the writing order.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a database recovery method, and is particularly applicable to an information processing system that has a large or medium-sized database and performs processing while updating the database. This invention relates to a database recovery method for emergency database recovery in the event of an emergency.

[Conventional technology]

In order to restore a database destroyed by a failure to the state before the failure occurred, each time the database is updated, the updated data of the updated part is stored as journal data in a temporary external medium such as a magnetic disk, and this data is stored in a temporary external medium such as a magnetic disk. - When the external medium becomes full, the data is collected and saved on an external storage medium such as magnetic tape. When a failure is recovered and the database is restored, the data at the start of operation that is stored on the external storage medium is first stored. The database is restored to the state before the failure occurred by loading the data into the database and updating it using the journal data collected on the storage external medium.

In conventional database recovery methods, when creating a journal for storage by collecting updated data from a magnetic disk onto a magnetic tape, all data in a file is read from the magnetic disk in chronological order onto the magnetic tape and collected. ing. When updating a database from its initial state to the state before a failure occurred, it is common to read all the data stored on the magnetic tape in order from the beginning and write it to the database for recovery.

[Problem to be solved by the invention]

In the conventional database recovery method described above, all updated data is collected on a magnetic tape and a journal is created, so there is a drawback that the amount of data to be stored is large, and therefore the amount of magnetic tape used is also large. Furthermore, when restoring a database, all the journal data stored on the magnetic tape is written from the beginning and the database is restored in chronological order, which is a disadvantage in that it takes a very long time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a database recovery method that reduces the amount of journal data collected on an external storage medium such as a magnetic tape and allows database recovery to be performed at high speed.

[Means to solve the problem]

The database recovery method of the present invention includes a database update means that stores the updated data of the updated part in a temporary external medium such as a magnetic disk every time the database is updated, and a database update unit that stores the updated data of the updated part in a temporary external medium such as a magnetic disk, and A journal collection means that reads backwards from the data and collects only the latest time data of the same file and the same block into a journal file on a storage external medium such as a magnetic tape, and when the database is restored after a failure, the journal file is stored. The system is configured to include a recovery processing means that sequentially reads each journal file from the beginning in the reverse order of the chronological order in which it was created, and writes only the latest time data of the same block of the same file to the database.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, ■ is the old database before the failure occurred, and is composed of file A and file B. 2 is a database update means, 3 is a disk file that stores updated data for each update, 4 is a journal collection means, 5 is a magnetic tape that collects journal files, 6 is a recovery processing means, 7 is an old database at the time of starting operation The database backup tape 8 stores the contents of 1, and the new database after recovery.

FIG. 2 is an explanatory diagram of the data processing procedure in this embodiment. In the figure, numerals 31 to 33 indicate disk journal data accumulated in the disk file 3 by the database updating means 2, and are the first to third accumulated in chronological order, respectively.

51 to 53 are tape journal data collected in the journal file of the magnetic tape 5 by the journal collection means 4, and 81 is a new database 8 created by the recovery processing means 6.
This is update journal data indicating the recovery order.

The database recovery operation will be described below with reference to FIGS. 1 and 2.

Before starting operation, first save the initial state of the old database 1 to the database save tape 7.
Every time the database is updated, the database updating means 2 writes the updated data of the updated portion into the disk file 3 in the order of occurrence, thereby obtaining the disk journal data 31 to 33 shown in FIG. 2. In Figure 2, the circled numbers such as ■ and ■ indicate the order in which they were written, and the symbols such as A2 and 85 indicate that the updated data of file A block number 2 and file B block number 5 in the database is stored. 9 When the disk file 3 becomes full, the journal collection means 4 writes the disk file 3 in the reverse order of writing.
The data is read out and stored on the magnetic tape 5. That is, the disk journal data 31 to 33 shown in FIG.
Instead of reading all the data from the beginning, it reads from the last data in reverse chronological order. Furthermore, when writing to the magnetic tape 5, only the data found earlier in the same file and the same block number is written. As a result, for data in the same file with the same block number, only the data with the latest generation time is written, and data with earlier times are not written, and disk journal data 31-33 are replaced by tape journal data 51-55, respectively.
It becomes 3.

That is, the magnetic tape 5 is collected by the journal collecting means 4.
The amount of data in the journals created will be significantly reduced.

Next, a procedure for restoring a failed database using the journal created in this way will be explained.

First, file areas for files A and H are secured on the new database 8, and the database at the start of operation is restored from the database backup tape 7. Next, the recovery processing means 6 reads the data of each journal file in the reverse order of creating the journal, that is, first reads the tape journal data 53 in FIG. 2, and then reads the tape journal data 52 and 51. The tape journal data, which is read in order, has already been written in the reverse chronological order, so the data is read from the beginning of each tape journal data and the corresponding block of the corresponding file in the database is rewritten. At this time, even if data of the same file and the same block as that updated by the tape journal data 53 exists in the tape journal data 51 and 52 to be processed later, the database will not be updated with that data. The update data journal 81 shows the order in which the database is actually updated in this way.

When all the tape journal data 51 to 53 are read out as described above and writing of the updated journal data 81 to the database is completed, the database restoration is completed.

As described above, the recovery processing means 6 updates the database with updated data at the latest time, and there is no need to process data in the same file and block again, so the amount of processing to actually rewrite the database is small. The processing time will be reduced accordingly.

Note that since the amount of data written from the disk file 3 to the magnetic tape 5 has been significantly reduced, it is possible to create multiple journal files on a single tape, but when writing, the data will be used starting from the later part of the tape. By doing so, it is convenient to read out and the recovery process can be performed even faster.

〔Effect of the invention〕

As explained in detail above, the present invention reduces the amount of data accumulated from a temporary external medium such as a magnetic disk to an external storage medium such as a magnetic tape, and furthermore reduces the amount of data processed when restoring a database from the external storage medium. We are also reducing
This has the effect of reducing the amount of magnetic tape used and allowing database recovery to be performed at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a data processing procedure in this embodiment. 1... old database, 2... database update means, 3... disk file,
4...-Journal collection means, 5...-Magnetic tape, 6...Return day processing means, 7...
...Database backup tape, 8...New database, 31-33...Disk journal data, 51-53...Tape journal data, 81...Update Jhana I Redata.

Claims (1)

[Claims] A database updating means stores the updated data of the updated part in a temporary external medium such as a magnetic disk each time the database is updated, and reads the data on the temporary external medium backward in chronological order starting from the last data and reads the data in the same file. For the data of the same block, there is a journal collection means that collects only the latest time data into a journal file on an external storage medium such as a magnetic tape, and when the database is restored after recovery from a failure, the journal file is stored in the chronological order in which it was created. A database recovery method characterized by comprising a recovery processing means that reads each journal file in reverse order from the beginning and writes only the latest time data of the same block of the same file to the database.