JPH0462095B2 - - Google Patents

Description

Detailed Description of the Invention [Summary] In a data processing system that has the function of managing a database consisting of an index file and a data file such as VSAM, a part of the data in the database is damaged due to a hardware failure. If this occurs, the damaged part of the database can be directly repaired without using the recovery function by database backup, so that the data other than the damaged part can be used in the latest state.

[Industrial application field]

The present invention provides a database repair processing method that provides a simple repair function for a database whose data has been damaged due to a hardware failure in a data processing system that has the function of managing a database consisting of an index file and a data file such as VSAM. It is related to.

[Conventional technology]

Manage the database with a data processing device,
As a method of providing access method, so-called
VSAM (Virtual Storage Access Method) is used. This type of database has an index file and a data file that stores the data pointed to by the index file. Within the data file, records are organized in logical units called control intervals (CIs). is being managed.

By the way, if some of the data in the database is damaged due to a hardware failure, the contents of the database are generally restored using backup information that has been saved in advance and update log information. Recovery is done.

However, frequently collecting backups requires a great deal of time and effort, and sequentially obtaining update log information during online service increases system load. Some users use databases with specifications that do not keep update logs. In such cases, if part of the data in the database is damaged due to a hardware failure, the entire database must be discarded.

[Problem that the invention seeks to solve]

In the case of files with relatively simple organization, such as so-called direct organization files, even if part of the data is damaged, it is easy to restore the other parts so that they can be used as is. However, in the case of a database consisting of index files and data files, including alternative indexes such as VSAM, if some of the data is damaged, inconsistencies with various data management information will occur. Data cannot be used.

The present invention aims to solve the above problems, and without using the conventional recovery function using backup etc.
The purpose is to provide a database repair processing method for repairing a database.

[Means for solving problems]

FIG. 1 shows an example of the basic configuration of the present invention.

In FIG. 1, 10 is a processing unit consisting of a CPU and memory, 11 is an application processing unit that executes a program for processing data, 12 is a database management unit that provides database management functions, and 13
14 is a database access unit that accesses the database; 14 is a failure detection unit that detects hardware failures due to database access; 15
16 is a database repair unit that provides a database repair function according to the present invention; 16 is a damaged logical unit detection unit that accesses each predetermined logical unit, which is a unit of logical data input/output, for the faulty database and detects a damaged location; 17; a damaged block detection unit 18 that accesses the detected damaged logical unit in units of physical blocks and detects a damaged block;
is a replacement area allocation unit that allocates a replacement block or track for the detected damaged block;
19 is a record management information repair unit that repairs record management information in a damaged logical unit; 20 is a unit that checks consistency between an index file and a data file, and retrieves key values or relative record number information regarding records lost due to failure; 21 is an index file regeneration unit that regenerates an index file based on the restored data file; 22 is an output device such as a printer or an external storage device; 23 is an index such as an alternative index. File 24 represents a data file having data records in each logical unit of a predetermined length.

The application processing unit 11 is the database access unit 1
The data file 24 is created using the macro provided by 3.
If a hardware failure occurs at that time, the failure detection unit 14 detects the failure. The database repair unit 15 is activated by the failure detection unit 14 or by input of a repair command from an operator.

The database repair unit 15 activates the damaged logical unit detection unit 16. The damaged logical unit detection section 16
A macro provided by the database access unit 13 sequentially accesses the data file 24 from the first logical unit. When a failure is detected for that access and a damaged logical unit is found, the damaged block detector 17 is called.

The damaged block detection unit 17 detects a damaged physical block by directly accessing the physical block in the logical unit using a so-called EXCP macro or the like. Alternate area allocation unit 18
By assigning a replacement block or replacement track to the detected physical block,
Secure a replacement area for the damaged physical block.

The record management information restoration unit 19 guarantees consistency between control information and record information in logical units by converting records related to damaged physical blocks into so-called deleted records.

The lost record information output unit 20 determines whether or not there is a record pointed to from the index file 23 based on the original index file 23.
A process of checking consistency and outputting a list of key values or relative record number information, etc. regarding records lost due to a failure to an output device 22 such as a printer is executed.

The index file regeneration unit 21 regenerates the index file 23 from the data file 24 from which records related to the failure have been deleted. To recreate index file 23,
Commands provided by the conventional database management unit 12 can be used.

[Effect]

According to the present invention, the replacement area allocation unit 18 allocates an alternative area to the physical block detected by the damaged block detection unit 17, and the record management information restoration unit 19 allocates an alternative area.
Since control information is written to invalidate the record related to the damaged physical block, data other than the damaged portion is saved in the latest state.

For the user, the lost record information output unit 2
0 reports information such as key values related to the lost record, so the user can later restore the faulty data by re-entering the data of that record from, for example, a terminal device.

Since the index file regeneration unit 21 guarantees the consistency between the index file 23 and the data file 24, the data other than the damaged portion, which is saved in the latest state, can be accessed normally.

In particular, since there is no need to restore from backup information or update log information, it is possible to perform partial repairs directly while the system is running, for example by controlling exclusive locks only on the repaired area, and recovery can be done by stopping the system as in the past. Since there is no need to perform this process, the effects of failure can be kept to a minimum.

〔Example〕

Fig. 2 is an explanatory diagram of the control interval format, Fig. 3 is an explanatory diagram of detection of damaged CIs, and Fig. 4 is an explanatory diagram of repair processing in units of CIs.
FIG. 5 shows a processing explanatory diagram of an embodiment of the present invention.

In the following description of the embodiment, an example will be described in which it is applied to a database processing system using VSAM.
It can be applied not only to VSAM but also to database processing systems that manage index files and data files with similar formats.

In VSAM, the control interval (CI) shown in Figure 2 is used as a unit to control data transfer between the input/output buffer and the VSAM data set.
is used. The control interval is
It is a logical unit for data storage to increase independence from physical devices, and has a record storage area and a control information area for record definition fields (RDFn) and control interval definition fields (CIDF).

When a hardware failure is detected by accessing the data file 24 shown in FIG.
As shown in the figure, damage control interval detection is performed.

That is, reading is performed in control interval units sequentially from the beginning of the data section, and when an I/O error or format error occurs, it is determined that it is a damage control interval, and repair processing is started in control interval units. Note that the format error is related to the state in which a replacement block has been allocated, and in this case, CI format/record format repair processing is performed.

Repair processing in control interval units is
As shown in FIG. 4, a damaged physical block is first detected by accessing each physical block sequentially from the beginning of the damage control interval. If a damaged physical block is found, a replacement block (or replacement track) is assigned to that block. When the allocation of replacement blocks, etc. to the damaged physical block is completed, the CI format/record format restoration process is performed.

Restoration of the CI format/record format is a process to eliminate inconsistencies between the data record section and the control information section shown in FIG. 2, and the repair method differs depending on the damaged location. If the physical block containing CIDF and RDFn is damaged, all data within the control interval will be invalidated. If a physical block of a data record is damaged, the corresponding record is invalidated. That is, the record is treated as a deleted record, for example. If a physical block with only free space is damaged, there is no need to repair the CI format/record format.
If the storage attribute is FREE, after the CI format/record format is repaired, all management chains of deleted records in the database are reallocated.

Through the above processing, the data file 24 shown in FIG. 1 has been formally restored, but this alone causes a conflict with the index file 23. That is, index file 2
3 has information such as keys and positions within the data file 24, but some of the data files 24 are missing records due to repair processing of damaged locations.

In order to resolve this contradiction, by using the ALTER function of the so-called CRTDB command provided by the VSAM management department, the index file 2
3. Execute the regeneration process. This collects the contents to be stored in the index file 23 based on the data file 24, and stores the contents in the index file 23.
This is the process of remaking 3.

FIG. 5 shows the above processing in the form of a flowchart. Processing number in the following explanation ~
correspond to the numbers ~ shown in FIG.

When a hardware failure occurs in the data file 24 and repair processing is started by specifying the database name, system name, etc. using an operator command, first, the key length/record length of the database, storage Obtain information necessary for repairing attributes, etc.

Determine whether access to all control intervals (CIs) in the next process has been completed. When finished, control is transferred to processing.

The data file 24 is sequentially accessed in CI units from the beginning using the VSAM macro.

Determine whether an error occurred while accessing the CI. If it is normal, control is returned to the process.

For the CI in which an error has occurred, it is determined whether access to all physical blocks in the next process has been completed. When finished, control is transferred to processing.

All physical blocks in the damaged CI are accessed sequentially from the beginning using the EXCP macro.

Determine whether an error has occurred. If no error occurs, return to the process and repeat the process for the next physical block.

If an error occurs, a replacement block or track is allocated and the process returns.

Execute the CI format/record format repair process,
Thereafter, the process returns to repeat the process for the next CI.

When the restoration of the data file 24 is completed, the consistency between the index file 23 and the data file 24 is checked according to the index file 23.

If the index file 23 has a key value, etc., but the data file 24 does not have a corresponding record (a record that existed in the damaged area), it is extracted as a lost record.

Outputs a list of lost record information to a specified device such as a printer, display, or external storage device.

The index file 23 is recreated by using the ALTER function of the CRTDB command.

Records lost due to hardware failure will be notified to the user through the list output of the above process, so the user can then completely restore the database by re-entering the data for that record. It is. For example, in the case of an employee management database, the employee number or name is output as a list as a key value, so the key value can be used to retrieve the employee's data including department, age, address, and other information. Just put it back in.

〔Effect of the invention〕

As described above, according to the present invention, a database can be easily repaired without using a conventional recovery function that uses backup and update logs. Since there is no need to acquire logs for recovery, DASD resources and CPU resources can be used effectively during service. Since partial repair is performed directly on the damaged area, the repair process can be performed without stopping the system.

[Brief explanation of the drawing]

Fig. 1 is an example of the basic configuration of the present invention, Fig. 2 is an explanatory diagram of the control interval format, and Fig. 3 is an explanatory diagram of the format of the control interval.
FIG. 4 is a diagram for explaining detection of damaged CIs, FIG. 4 is a diagram for explaining repair processing in units of CIs, and FIG. 5 is a diagram for explaining processing in an embodiment of the present invention. In the figure, 10 is a processing device, 11 is an applied processing unit, 1
2 is a database management section, 13 is a database access section, 14 is a failure detection section, 15 is a database repair section, 16 is a damaged logical unit detection section, 17 is a damaged block detection section, 18 is a replacement area allocation section, 1
Reference numeral 9 represents a record management information restoration unit, 20 represents a lost record information output unit, 21 represents an index file regeneration unit, 22 represents an output device, 23 represents an index file, and 24 represents a data file.

Claims (1)

[Scope of Claims] 1. Data processing for handling a hardware failure of a physical block on a secondary storage device regarding a VSAM format database consisting of an index file 23 and a data file 24 pointed by the index file 23. The system includes means 16 for sequentially accessing the data file 24 in which a failure has occurred from the beginning for each predetermined logical unit, which is a unit of logical data input/output, to detect a damaged location; means 17 for detecting a damaged logical unit by accessing it in physical block units; means 18 for allocating a replacement area for the detected damaged block; and means 19 for restoring record management information in the logical unit. and means 20 for checking the consistency between the index file 23 and the data file 24 repaired by each of the above means, and outputting key value or relative record number information regarding records lost due to a failure; 23 based on the restored data file 24.