JPH0820992B2 - Control journal output device - Google Patents

Description

The present invention relates to a control journal output device for performing recovery in a data processing system in which a plurality of tasks share a plurality of databases and execute processing.

[Prior Art] Conventionally, in a data processing system in which a plurality of tasks share and process a plurality of databases, the recovery after the system is down is updated halfway because transaction execution is aborted midway. By using the database pre-update information record accumulated in the journal file to write back the database, the database is restored to the state before the transaction is started for all incomplete transactions.

[Problems to be Solved by the Invention] In this conventional data processing system, in order to confirm that all incomplete transactions have been recovered, transaction processing is being performed for all tasks or transaction processing is being performed. It was necessary to record in the control file as transaction execution status information so that it was possible to identify whether the transaction was incomplete when the system went down. However, the method of using the control file in addition to the journal file has to set two types of information storage processing and two types of files to restore the database, and there is a problem that the efficiency of the database restoration processing is low. .

Therefore, an object of the present invention is to be able to properly and efficiently execute restoration processing of a database updated by a transaction that has become incomplete due to system down.

[Means for Solving Problems] A control journal output device according to the present invention includes a transaction execution state management table on a memory in which information indicating whether a transaction is being executed is written for each transaction, and the start of the transaction. At the end and at the end, the transaction start information record and the transaction end information record are output as journal records, and when the transaction updates the database 4, the transaction pre-update information record that is the content before and after the update of the database And a post-transaction update information record as journal records, and a journal output control unit 2b that outputs the transaction execution state management table as an active point journal record at an arbitrary time, and a system down. When the system restarts, the journal record output immediately before the system down is read one by one from the journal records output before that, and when the transaction updated information record is read, the transaction updated information is read. When the database 4 is restored based on the transaction pre-update information record corresponding to the record and the transaction end information record is read out, the database pre-update information related to the transaction that has output the transaction end information record If the record, the post-database update information record, and the transaction start information record are skipped and the activity point journal record is read, the The transaction execution status management table restored to the memory, the transaction in the transaction execution state management table has finished process when the in a non-running,
For a transaction that is determined to be being executed in the transaction execution state management table and for which the transaction end information record has not been read by the time the activity point journal record is read, from that point until the transaction start information record is read. After the database 4 is restored based on the pre-database-update information record and the post-database-update information record that are read, the processing is terminated, and the active-point journal record is read when all the journal records are read. If it does not exist, a recovery control unit 2c for ending the process is provided.

Embodiments Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a control journal output device according to the present invention. In this embodiment, the application program 1
It is composed of a journal file 3, a database 4, and a control journal output device including a database access control unit 2a, a journal output control unit 2b and a recovery control unit 2c.

The transaction execution state management table (not shown) on the memory stores 1 for each transaction and 0 if the transaction is being executed.

The journal output control unit 2b receives a transaction start information record when the application program 1 that performs transaction processing starts execution, and a database pre-update information record and a database post-update information record when the database 4 is updated. When the execution of the application program 1 that performs the transaction processing ends, the transaction end information record is output to the journal file 3. Further, the active point journal record storing the transaction execution state management table is asynchronously output to the journal file 3.

When the system goes down, the recovery control unit 2c starts reverse reading from the last journal record output to the journal file 3 and writes back the database 4 using the pre-database update information record. In this recovery processing, when the active point journal record is read, the transaction execution state management table is restored, and the transaction start information record and the transaction end information record output to the journal file 3 before the active point journal record is output. When it is read, the contents of the transaction execution state management table are updated, and it is determined that the database updated by all uncompleted transactions has been restored to the state before update by using this management table, and the recovery processing is performed. Complete.

Next, an example of recovery processing in this embodiment will be described with reference to the time chart of FIG.

Next, an example of recovery processing in the present invention will be described with reference to the time chart of FIG.

The jobs being executed in the system are RON10 and RON11 jobs.
It is assumed that there are tasks T1 and T2, tasks T3 and T4, and the system is down at time t3. Recovery control executed after system
Reverse reading is started from the final output journal record at time t3, and transaction TR2 is incomplete, so database 4 is written back using the database pre-update information record of this transaction TR2. Since the transaction end information record of the transaction TR1 executed in the task T1 is detected in the middle of the reverse reading, all the information records before the database update and the information records after the database update of the subsequent task T1 are skipped. At time t2, the active point journal record is read from the journal file 3 and the transaction execution state management table is restored. From this management table, at time t2, it is determined that there are two jobs in the system, that is, RON10 and RON11, and that there are no incomplete transactions in tasks T3 and T4. For transaction TR1 in which the transaction end information record is being read during the backward reading of the journal file,
The transaction is complete and there is no need to write the database back. For this reason, all the information records before the database update and the information records after the database update of transactions TR1 and TR3 are skipped, and transaction TR2
Transaction TR2 at time t1 while writing back database 4 with the information record before updating the database
When the transaction start information record of is read, the recovery processing is completed for all uncompleted transactions.

[Effects of the Invention] As described above, the present invention provides the transaction execution state management table for managing the transaction execution states of all tasks in the system, and asynchronously outputs this to the journal file as an active point journal record, In the recovery process after the system goes down, the database is written back by the pre-update information record of the incomplete transaction while performing the reverse reading of the journal file, and at the same time, the transaction execution state management table is restored from the active point journal record, and the active point is restored. When the transaction start information record and transaction end information record output before the journal record output is read, the contents of the transaction execution status management table are updated and this task is executed by all tasks. The transaction execution status is determined because it is determined that the unfinished transaction that has been restored has been recovered, and that the database updated by the database pre-update information record of the unfinished transaction has been written back and the recovery has ended. Compared with the conventional technique that outputs the management table to the control file, the database restoration process can be executed properly and efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the control journal output device of the present invention, and FIG. 2 is a time chart showing an example of recovery in FIG. 1 ... Application program, 2 ... Control journal output device, 2a
... database access control unit, 2b ... journal output control unit, 2c ... recovery control unit, 3 ... journal file,
4 ... Database.

Claims (1)

[Claims] 1. A transaction execution state management table on a memory for writing information indicating whether or not a transaction is being executed, a transaction start information record and a transaction end information record at the start and end of the transaction. Is output as a journal record, and when the transaction updates the database 4, the pre-update information record and the post-transaction update information record, which are the contents before and after the update of the database, are output as journal records. , A journal output control unit 2b that outputs the transaction execution state management table as an active point journal record at an arbitrary point, and at the time of restarting after a system down, it is output immediately before the system down When the transaction updated information record is read one by one from the journal record output to the previously output journal record, the transaction updated information record is read based on the transaction updated information record corresponding to the transaction updated information record. When the database 4 is restored and the transaction end information record is read, thereafter, the database pre-update information record, the database post-update information record, and the transaction start information relating to the transaction that output the transaction end information record. If you skip the record and read the activity point journal record,
The transaction execution state management table is restored in the memory based on the activity point journal record, and when the transaction is not in execution in the transaction execution state management table, the processing is terminated, and the transaction execution state management is executed. The database update that is read in the table and is read from the transaction start information record until that transaction end information record is not read by the time the activity point journal record is read. After the database 4 is restored based on the previous information record and the information record after the database update, the process is terminated, and the active point journal record is not read when all the journal records are read. The control journal output device 2 is provided with a recovery control unit 2c for ending the processing.