JP4730330B2 - Database recovery method, database recovery device, and database recovery program - Google Patents

Description

  The present invention relates to a database recovery method, a database recovery apparatus, and a database recovery program, and more particularly to a database recovery method, a database recovery apparatus, and a database recovery program capable of recovering a consistent DB.

  As a management system for a conventional database (hereinafter referred to as “DB”), a DB delayed update method based on a journal file in which DB backup is executed using a single journal file has been proposed (for example, Patent Document 1). reference).

Also, when a failure occurred in both the DB and the journal due to an earthquake or fire, the data was backed up without interruption.
JP 2000-112807 A

  However, as described above, when the base journal and the cumulative journal are backed up without interruption, both the base journal and the cumulative journal are backed up asynchronously. There was a problem that it could not be determined.

  An example of an operation in which a DB cannot be recovered from a backup of a DB or journal that is not suspended will be described with reference to the drawings. FIG. 11 shows an example of backing up a conventional journal record, in which the base journal is a journal record surrounded by a dotted frame g, the cumulative journal is a journal record surrounded by a dotted frame h, and the DB is surrounded by a dotted frame i. Suppose the state has been backed up. FIG. 12 shows a state where such a backup is restored.

  The roll-forward recovery operation will be described with reference to FIG. 13. As roll-forward recovery, DB records R1 and R2 are overwritten using journal records 35, 36, and 37 on the cumulative journal. After this, since there is an incomplete transaction (T3) for which the transaction end journal (“T3 end”) has not been output in the base journal, it is necessary to perform rollback recovery.

  The rollback recovery operation will be described with reference to FIG. 14. The journal record 38 on the base journal becomes a journal record to be rolled back, and the DB record R1 is overwritten based on the record of the journal record 38.

  The state shown in FIG. 14 after the completion of the rollback recovery is the recovery using the journal backed up without stopping the business. However, in the records R1 and R2 of the DB, all journal records are backed up to the base journal and the cumulative journal. However, the journal recovery process completes the recovery in a state different from that at the end of the transaction T1, and the DB becomes inconsistent.

  Therefore, as a countermeasure against simultaneous failure of the DB and the journal due to an earthquake or a fire, a backup at a stationary point is required instead of a backup without stopping business. In addition, the above-mentioned DB inconsistency is that the restored base record and the cumulative journal are not added with serial numbers for confirming the relationship between them, so that the restored journal record can only be passed to the journal recovery means as it is. This is a problem that arises.

  The present invention has been made in view of such circumstances, and aims to recover from failures of both the DB and the journal by adding serial numbers for confirming the relationship between the base journal and the cumulative journal. The purpose of this is to recover a consistent DB without stopping business.

  According to the first aspect of the present invention, there is provided a base journal storage step for storing a database data file as a journal record at a predetermined time point, and a journal after update when the journal record stored in the base journal storage step is updated. A cumulative journal storage step for storing records, the base journal storage step, a serial number addition step for adding serial numbers to journal records stored in the cumulative journal storage step, the database, a base journal storage step, and the cumulative A backup step for backing up data included in the journal storage step to a storage medium, and a restore step for performing restoration from the storage medium to the database, the base journal storage step, and the cumulative journal storage step. And a recovery step for recovering the database based on the data of the restored database, the base journal saving step, and the cumulative journal saving step, and the journal added by the serial number adding step at the time of recovery by the database recovery step The serial number confirmation step for confirming the serial number of the journal record using the serial number of the record, and the recovery subject to the recovery step only when it can be confirmed that all the journal records are prepared by the serial number confirmation step. A database restoration method comprising: an availability determination step.

  According to a second aspect of the present invention, in the method according to the first aspect of the present invention, the method further comprises a recovery effective range determining step for determining an effective range of journal records used for recovery by the recovery step, wherein the serial number confirmation step is the determined The serial number of the journal record within the valid range is confirmed, and the recovery enable / disable step confirms that all the serial numbers of the journal record within the determined valid range are prepared, and recovery within the valid range is possible. It is characterized by determining whether or not.

  According to a third aspect of the present invention, in the method according to the second aspect, the valid range is a range from a transaction start journal record to a corresponding transaction end journal record.

  According to a fourth aspect of the present invention, in the method according to the second or third aspect, the recovery effective range determining step scans journal records in reverse order when all the serial numbers are not aligned within the effective range, The following effective range is determined.

  According to a fifth aspect of the present invention, in the method according to any one of the first to fourth aspects, the storage medium for backing up data by the backup step is an external storage medium.

  According to a sixth aspect of the present invention, there is provided a base journal storage unit that stores a database data file as a journal record at a predetermined time point, and a journal that has been updated when the journal record stored in the base journal storage unit is updated. Cumulative journal storage means for storing records, the base journal storage means, serial number addition means for adding serial numbers to journal records stored in the cumulative journal storage means, the database, base journal storage means, and cumulative A backup unit that backs up data stored in the journal storage unit to a storage medium; a restore unit that performs a restore from the storage medium to the database, the base journal storage unit, and the cumulative journal storage unit; and the restored database and the base journal Null storage means, recovery means for recovering the database based on the data of the cumulative journal storage means, and at the time of recovery by the recovery means of the database, using the serial number of the journal record added by the serial number addition means, the journal record A serial number confirmation unit that performs serial number confirmation, and a recovery possibility determination unit that is a target of the recovery unit only when it is confirmed by the serial number confirmation unit that all journal records are prepared. It is a database recovery device.

  According to a seventh aspect of the present invention, there is provided a base journal storage process for storing a database data file as a journal record at a predetermined time point, and a journal after the update when the journal record stored in the base journal storage process is updated. Cumulative journal storage processing for storing records, base journal storage processing, serial number addition processing for adding serial numbers to journal records stored in the cumulative journal storage processing, the database, base journal storage processing, and cumulative Backup processing for backing up data included in the journal storage processing to a storage medium, restore processing for performing restoration from the storage medium to the database, the base journal storage processing, and the cumulative journal storage processing, and the restored database and base journal Null save process, recovery process for recovering the database based on the data of the accumulated journal save process, and a journal record using the serial number of the journal record added by the serial number adding process at the time of recovery by the recovery process of the database The computer executes the serial number confirmation process for confirming the serial number and the recovery possibility determination process that is the target of the recovery process only when it is confirmed that all journal records are prepared by the serial number confirmation process. This is a database recovery program.

  According to the present invention, by adding serial numbers to the journal records output to the base journal and the cumulative journal, a consistent DB is recovered by using the backup of the DB collected without stopping and the journal. Make it possible.

  In the present invention, in a transaction processing system in which a base journal and a cumulative journal are separately configured, when a failure occurs in both the DB and the journal due to an earthquake or a fire, the DB and the journal are stopped without interruption. Even if the database is backed up, a consistent DB is recovered. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.

  First, a transaction processing system to which the present invention is applied will be described. FIG. 1 associates the flow of transaction processing with the operation processing of the base journal, cumulative journal, DB record (R1), and DB record (R2). As shown in FIG. 1, the transaction processing system to which the embodiment of the present invention is applied is a transaction processing system in which the base journal and the cumulative journal are configured as separate files.

  Here, the journal is a history of update information recorded by the system while the computer system is running. This record is used to investigate the cause and recover when the system fails. used. In this embodiment, in order to improve the output performance of the journal and expand the capacity, the journal is managed by being distributed to the base journal and the cumulative journal. For the base journal, each journal record (FIG. 1, “R1: Start of T (Transaction) 1”), transaction end (FIG. 1, “T (Transaction) 1 end”), and pre-update image journal records. X "" R2: Y ") is output, and the journal record of the updated image (" R1: A "" R2: L ") is output to the cumulative journal.

  A feature of the present invention is that serial numbers are added to journal records output to the base journal and the cumulative journal, and FIG. 2 shows an output example of journal records to which such serial numbers are added.

  FIG. 3 shows a block diagram of the host computer 1 according to the embodiment of the present invention. In addition to the host computer 1, FIG. 3 also shows an external medium 13 that holds save data for the DB, base journal, and cumulative journal.

  The host computer 1 includes a transaction control unit 2, a DBMS (database management system) 3, a serial number storage area 4, a serial number addition unit 5, a journal output unit 6, a journal recovery unit 7, The journal effective range determination unit 8, the backup / restore unit 9, the cumulative journal 10, the base journal 11, and the DB 12 are configured.

  The transaction control unit 2 controls the execution of the transaction and notifies the DBMS 3 of the journal output. The DBMS 3 controls the input / output of the DB, the base journal, and the cumulative journal in cooperation with the transaction control unit 2.

  The serial number adding unit 5 uses the serial number stored in the serial number storage area 4 to add a serial number that is incremented by 1 for each output of one journal record to the journal record.

  The journal output unit 6 outputs journal records to the cumulative journal 10 and the base journal 11.

  The journal recovery unit 7 recovers the DB 12 based on the journal records of the cumulative journal 10 and the base journal 11.

  The journal effective range determining unit 8 refers to the serial number added to the journal record by the serial number adding unit 5 and determines the range of journal records used when the journal recovery unit 7 performs recovery.

  The backup / restore unit 9 backs up the cumulative journal 10, the base journal 11, and the DB 12 to the external medium 13, and restores (Restore) from the external medium 13 to the base journal 11, the cumulative journal 10, and the DB 12. Here, the term “restore” refers to returning the data created in the program creation to the original location, and specifically, restoring the backed up program or data.

  Next, operation processing of the DB restoration method according to the present embodiment will be described with reference to the drawings. First, a description will be given using a flowchart (FIG. 4) showing an operation process at the time of journal record output. When the journal output unit 6 outputs a journal record to the base journal 11 or the cumulative journal 10, the sequence number adding unit 5 reads the current sequence number stored in the sequence number storage area 4 (step S1), and step S1. 1 is added to the serial number acquired in step S2 (step S2), the journal record output from the journal output unit 6 is written to the journal record (step S3), and the journal record to which the serial number is added in step S3 The data is output to the journal 11 or the cumulative journal 10 (step S4), and the currently held serial number is written to the serial number storage area 4 (step S5).

  Non-stop backup is backed up to the external medium 13 using the backup / restore unit 9. The operation of backing up the DB and journal is shown in FIG. In FIG. 5, it is assumed that the base journal is a journal record enclosed by a dotted frame a, the cumulative journal is a journal record enclosed by a dotted frame b, and the database is backed up by the external medium 13 in a state enclosed by a dotted frame c. . The following description is also made on the assumption of the backup state shown in FIG.

  Next, DB recovery processing will be described with reference to a flowchart (FIG. 6). When performing DB recovery, restore from the external medium 13 to the cumulative journal 10, the base journal 11, and the DB 12 using the backup / restore unit 9 (step S6), and recovery using the journal effective range determination unit 8 The range of journal records to be used in the process is determined (step S7), and the recovery of the DB 12 is performed using the journal recovery unit 7 with respect to the range of the journal record determined in step S7 (step S8), and the recovery of the DB 12 is completed. .

  Next, the process of determining the range of journal records used for recovery using the journal effective range determination unit 8 in step S7 will be described in detail with reference to the drawings. First, the end of the base journal is positioned (step S10 in FIG. 7), and the transaction end journal is scanned in reverse order (step S11).

  The operation of step S10 will be described with reference to FIG. As shown by the arrow in FIG. 8, the journal records 25 and 24 are skipped from the end of the base journal, the transaction end journal (“T2 end”) is found in the journal record 23, and the scan in step S10 in FIG. 7 is completed.

  Next, a transaction start journal (“T2 start”) corresponding to the transaction end journal (FIG. 8 journal record 23) found in step S10 is found, and all the journal records from the transaction start journal to the transaction end journal are complete. Check. That is, it is checked whether all serial numbers between the serial numbers of the transaction start journal and the serial numbers of the transaction end journal can be found from the restored journal record (step S12 in FIG. 7).

  The operation in step S12 will be described in detail with reference to FIG. Since the transaction start journal corresponding to the transaction end journal 23 becomes the journal record 20, serial numbers 8, 9, 10, 11 from the serial number 7 of the transaction start journal 20 to the serial number 12 of the transaction end journal 23 are changed. It will be checked whether it can be found from the journal records of the restored base journal and cumulative journal. In FIG. 8, since the journal record having the serial number 11 cannot be found, it is determined that the transaction T2 starting with the transaction start journal 20 and ending with the transaction end journal 23 is unrecoverable.

  If it is determined in step S12 that all the serial numbers are not complete (step S13 / No), the process returns to step S11 again, the transaction end journal is repeatedly scanned, and the step S12 is performed based on the found transaction end journal. Perform the inspection.

  In the serial number inspection shown in FIG. 8, since the serial number 11 was not found, it is necessary to scan the transaction end journal again in the reverse order. The operation after the transaction end journal is found again is shown in FIG. Since the transaction start journal (“T1 start”) corresponding to the found transaction end journal (“T1 end”) 30 is a journal record 27, the serial number 1 possessed by the transaction start journal 27 and the serial number 6 possessed by the transaction end journal 30 It is checked whether the serial numbers up to, that is, serial numbers 2, 3, 4, and 5 can be found from the restored journal records of the base journal and the cumulative journal.

  In FIG. 9, since all journal records having serial numbers 2, 3, 4, and 5 can be found (see journal records 28, 30, 29, and 31), the transaction T1 that starts with the transaction start journal 27 and ends with the transaction end journal 30 is The journal recovery unit 7 determines that recovery is possible.

  When it is confirmed in step S13 that all the serial numbers are aligned (step S13 / Yes), the effective range determination process (step S7 in FIG. 6) by the effective range determination unit 8 of the journal record ends, and the journal record The DB recovery by the journal recovery unit 7 is performed for the effective range (step S8 in FIG. 6).

  FIG. 10 shows an operation for performing journal recovery on the journal record of the transaction T1 determined to be the valid range in FIG. The journal records 33 and 34 of the cumulative journal are used for roll forward (Roll Forward; reflecting update information not reflected in the DB to the DB) recovery (Recovery; failure recovery), and the records R1 and R2 in the DB are overwritten. To do. Since the transaction T1 is a completed transaction for which a transaction end journal has been output, the recovery ends without performing rollback recovery (Rollback; seeing the log file and returning the DB to the state before the start of processing).

  According to the above embodiment, in a transaction processing system having a base journal and a cumulative journal, there is no need to stop the operation for backup for the purpose of recovery from a failure of both the DB and the journal due to an earthquake or a fire. The DB can be recovered by using the serial number added to the journal record from the DB and journal collected by the stop.

  Note that the program for the CPU to execute the processing shown in the flowcharts of the drawings constitutes a program according to the present invention. As a recording medium for recording the program, a semiconductor storage unit, an optical and / or magnetic storage unit, or the like can be used. By using such a program and a recording medium in a system having a configuration different from that of each of the above-described embodiments and causing the CPU to execute the program, substantially the same effect as the present invention can be obtained.

  Although the present invention has been specifically described above based on the preferred embodiments, it is needless to say that the present invention is not limited to the above-described ones and can be variously modified without departing from the gist thereof.

It is a figure which shows the flow of operation | movement of the transaction processing which concerns on embodiment of this invention, a base journal, an accumulation journal, DB record R1, and the operation | movement of DB record R2. It is a figure which shows the output example which added the serial number to the journal record output to the base journal and accumulation journal which concern on embodiment of this invention. It is a block block diagram of the host computer which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement process at the time of the journal record output which concerns on embodiment of this invention. It is a figure for demonstrating the operation | movement process which backs up DB and a journal which concern on embodiment of this invention. It is a flowchart which shows the operation processing at the time of recovery of DB which concerns on embodiment of this invention. It is a flowchart which shows the determination process of the range of the journal record utilized for the recovery using the journal effective range determination part 8 which concerns on embodiment of this invention. It is a figure for demonstrating scanning the transaction end journal which concerns on embodiment of this invention in reverse order. It is a figure for demonstrating the operation | movement after discovering the transaction completion journal which concerns on embodiment of this invention again. It is a figure for demonstrating the operation | movement which implements journal recovery with respect to the journal record of transaction T1 judged to be the effective range which concerns on embodiment of this invention. It is a figure which shows the example which backs up the conventional journal record. It is a figure which shows the state which restored the conventional backup. It is a figure for demonstrating the operation | movement of the conventional roll forward recovery. It is a figure for demonstrating the operation | movement of the conventional rollback recovery.

Explanation of symbols

1 Host computer 2 Transaction control unit 2
3 DBMS
4 Serial number storage area 5 Serial number addition unit 6 Journal output unit 7 Journal recovery unit 8 Journal effective range determination unit 9 Backup / restore unit 10 Cumulative journal 11 Base journal 12 DB

Claims (7)

A base journal storage step for storing a database data file as a journal record at a predetermined time;
A cumulative journal storage step for storing the updated journal record when the journal record stored in the base journal storage step is updated;
A base number adding step for adding a serial number to journal records stored in the base journal storing step, and the cumulative journal storing step;
A backup step of backing up data stored in the database, base journal storage step, and cumulative journal storage step to a storage medium;
A restore step for performing a restore from the storage medium to a database, a base journal saving step, and the cumulative journal saving step;
A recovery step of recovering the database based on the data of the restored database, the base journal storage step, and the cumulative journal storage step;
At the time of recovery by the recovery step of the database, using the serial number of the journal record added by the serial number addition step, a serial number confirmation step of performing serial number confirmation of the journal record,
A database recovery method comprising: a recovery possibility determination step that is a target of the recovery step only when it is confirmed that all journal records are prepared by the serial number confirmation step. A recovery effective range determining step of determining an effective range of journal records used for recovery by the recovery step;
The serial number confirmation step confirms the serial number of the journal record within the determined effective range,
2. The recovery enable / disable step confirms that all serial numbers of journal records within the determined effective range are prepared, and determines whether or not recovery within the effective range is possible. Database recovery method.   3. The database recovery method according to claim 2, wherein the valid range is a range from a transaction start journal record to a corresponding transaction end journal record.   4. The recovery effective range determination step, when not all serial numbers are aligned within the effective range, scans journal records in reverse order to determine the next effective range. Database recovery method.   5. The database recovery method according to claim 1, wherein the storage medium that backs up the data in the backup step is an external storage medium. Base journal storage means for storing a database data file as a journal record at a predetermined time point;
Cumulative journal storage means for storing the updated journal record when the journal record stored in the base journal storage means is updated;
Said base journal storage means; serial number addition means for adding serial numbers to journal records stored in said cumulative journal storage means;
Backup means for backing up the data stored in the database, base journal storage means, and cumulative journal storage means to a storage medium;
A restore unit for performing a restore from the storage medium to a database, a base journal storage unit, and the cumulative journal storage unit;
Recovery means for recovering the database based on data of the restored database, base journal storage means, and cumulative journal storage means;
At the time of recovery by the database recovery means, serial number confirmation means for performing serial number confirmation of journal records using the serial number of journal records added by the serial number addition means,
A database recovery apparatus comprising: a recovery possibility determination unit that is a target of the recovery unit only when it is confirmed by the serial number confirmation unit that all journal records are available. Base journal storage processing for storing database data files as journal records at a predetermined time point;
A cumulative journal storage process that stores the updated journal record when the journal record stored in the base journal storage process is updated;
A serial number addition process for adding serial numbers to journal records stored in the base journal storage process, and the cumulative journal storage process;
Backup processing for backing up data stored in the database, base journal storage processing, and cumulative journal storage processing to a storage medium;
A restore process for performing a restore from the storage medium to a database, a base journal save process, and the cumulative journal save process;
A recovery process for recovering the database based on the restored database, base journal saving process, and cumulative journal saving process data;
At the time of recovery by the recovery process of the database, using the serial number of the journal record added by the serial number addition process, a serial number confirmation process for performing serial number confirmation of the journal record,
A database recovery program that causes a computer to execute a recovery possibility determination process that is a target of the recovery process only when it can be confirmed that all journal records are prepared by the serial number confirmation process.

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