JPH0762833B2 - Exclusive control method for shared data set - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an exclusive control method for a shared data set, and more particularly, to access a data set such as a VSAM data set shared by a plurality of users in an online system, The present invention relates to a method of exclusive control with high online processing efficiency.

[Background of technology]

First, an example of the VSAM data set which is the subject of the present invention will be briefly described.

A VSAM (Virtual Storage Access Method) data set has a control interval, which is a data transfer unit, and a control area, which is composed of a plurality of control intervals, as a management unit.

The length of the control interval (hereinafter referred to as CI) is
It is determined for each data set and can be set up to a maximum size of 32,768 bytes. A record, which is an access unit of a user, is accommodated in one CI in principle, but it may extend over two or more CIs.

The maximum size of the control area (hereafter called CA) is 1
A cylinder is the smallest unit for expanding a data set. FIG. 1 conceptually shows a data set structure by CA and CI.

The types of datasets that can be supported by VSAM are key sequence data set KSDS and entry sequence data set.
These are ESDS and relative record data set RRDS.

Next, an example of a database system using the VSAM data set will be described with reference to FIG.

In FIG. 2, 1-1 and 1-2 are online terminals, 2 is a host, 3-1 and 3-2 are business programs, and 4 is an online database processing system AIM (Advanced Informat).
ion manager), 4a is an exclusive control unit, 5 is VSAM, 5a is an exclusive control unit, and 6 is a database stored in a file device such as a disk device. The database 6 is a VSAM data set, and CI1 to CI9 and CA7 to CI9 shown are CA2.
When expressed by relative CI numbers in the above, it becomes CI1 to CI3.

The users of the online terminals 1-1 and 1-2 have business programs 3-1 and 3-2, respectively, in order to process their own business.
To call a transaction that uses the database 6.

AIM analyzes the transaction and accesses the database 6 for the required record. The database 6 is accessed by accessing the corresponding CI via VSAM.

If a data access is intended for updating or addition, it guarantees to other data users the freshness of the data, that is, the data has been updated most recently, and In order to synchronize the update level of the data used by the users, it is necessary to prohibit other users from accessing the same data until the data access is completed.

For this reason, the exclusive control unit 5a of VSAM has an exclusive control function in CI units, and prohibits all other access to the CI while performing data update or data addition processing for a certain CI. I am trying. But 1
Access requests may be issued to multiple CIs from one transaction. For this reason, the AIM manages the guarantee of data in transaction units, and can detect even if a deadlock state occurs due to conflicting data access orders among multiple transactions. The exclusive control unit 4a
It is provided for this purpose.

An example in which data guarantee cannot be obtained in transaction units by exclusive control of VSAM will be explained with reference to FIG.
As illustrated in the figure, the business program 3-1
If the business program 3-2 has access requests in the order of CI1 → CI2, and the business program 3-2 has access requests in the order of CI2 → CI3, the exclusive control of VSAM causes the business program 3-1 to
While accessing CI1, CI2 of business program 3-2
Access is not exclusive and can be updated, for example. Therefore, the CI2 access of the business program 3-1 becomes an access to the CI2 data after being updated by the business program 3-2, and the update level consistency (or synchronism) with the CI1 data is lost. .

The exclusive control unit 4a of the conventional AIM performs exclusive control in CA units in order to solve the data guarantee problem in transaction units as described above. That is, in AIM-VSAM, a new CA is cut out (referred to as CA division) when the CA cannot store the records. At that time, since the end position of the data changes, this end position of the data is reflected as EOD (End of Data) information in other business programs accessing the same data set to guarantee the freshness of the data. ing. But in this case, it is not possible to predict when the CA split will occur, so
When data is updated / added to a CI, the entire CA including that CI is uniformly prohibited from access to any business program that accesses any CI in the same CA.

However, when exclusive control is performed in CA units as described above, for example, in the example of FIG. 2, the access target CIs of the business programs 3-1 and 3-2 are both included in the same CA1, so When the access request of the other business program is accepted, the access request of the other business program is kept waiting until the transaction processing is completed. Even if the CIs to be accessed do not conflict with each other, the CIs are excluded as long as they are in the same CA, which has conventionally been one cause of reducing the online processing efficiency.

Further, in the conventional method, the EOD is reflected by CPEN to capture the EOD information and CLOSE to reflect the EOD information. However, for example, in the case of online work, the work is usually started in the morning and finished in the evening, so the work program holds the first situation in the morning at the time of OPEN as EOD information. This does not guarantee the freshness of the data. Therefore, in the conventional method, if the EOD information may change due to CA division, once close the business program.
It was necessary to end it with and open it again. In this way, it is necessary to repeat OPEN-CLOSE to know the latest data, and initialization of OPEN processing takes time, so it was not suitable for online work.

[Object and Structure of Invention]

An object of the present invention is to reduce unnecessary access delay by providing means for reducing the range of exclusion target data set in the conventional exclusion control method to a more effective one, Therefore, the objective is achieved by more accurately checking the access conflict relationship and taking a time-limited countermeasure for CA division.

Thereby, the configuration of the present invention includes a plurality of online terminals,
The database 6 and the data set of the database 6 are hierarchically managed by a first division unit CI that is a transfer unit and a second division unit CA that is a higher level than the first division unit CI, and is managed for each first division unit CI. It comprises a data management means 5 for performing exclusive control and an online processing means 4 for analyzing access to the shared data set of the database 6 by analyzing a transaction input from an online terminal. Is being accessed by the second division unit CA, and the first division unit CI of the second division unit CA is subjected to exclusive control of the shared data set, and the data management means 5 is the second division unit CA.
Only during the division processing of the first division unit CA in the second division unit CA.
The feature is that the access to the division unit CI is exclusively controlled by the second division unit CA.

Example of Invention

 Hereinafter, details of the present invention will be described according to examples.

FIG. 3 is a block diagram of a system of one embodiment of the present invention,
This is an improvement of the database system described in FIG. In the figure, 3-1 and 3-2 are business programs, 4 are AIMs, 4a 'is an exclusive control unit, 4b is a transaction analysis unit, 5 is VSAM, 5a is an exclusive control unit, 5b is a CA division processing unit, 6 is a database stored in a file device such as a disk device, 7 is a CI management table provided in a common area of the memory, and 8 is EOD information provided in the common area of the memory. Here, the CI management table 7 is exclusive for each business program and each transaction.
It is used to indicate the CI, and the CA number and CI number of the data set accessed in the transaction are registered in the order of access. The EOD information 8 indicates the data end position of the data set by the CA number and the CI number, and is updated when the data end position changes due to the update of the data set. When the EOD information 8 is updated, the content is notified to each business program that uses the corresponding data set.
Each business program fetches the EOD information 8 at that time at the time of the OPEN processing as in the conventional case, and updates it when the new EOD information is notified. Note that the same reference numerals are used for those functionally corresponding to the constituent elements in FIG.

The transaction analysis unit 4b of the AIM analyzes the data access request for each transaction of the accepted business program, and registers the corresponding CA number + CI number of the corresponding CA in the CI management table 7. Business program (3-1)
When the business program (3-2) adds a record to CA1 while obtaining and processing the data of CI1 and CI2 of CA1, CA1 becomes full and CA split occurs, that is, the third In the example in the figure, I tried to add CI7 to CI9 to CA1, but CA1
If there is no free space in and CA split occurs, CA2 is created. This added data of CI7 to CI9 is CA2 + CI1
Converted to the relative CI number in CA2 as ~ CA2 + CI3, C
It is registered in the I management table 7. This CA
While the data corresponding to CI7 to CI9 exist during the division, the CA division is completed because the record does not exist when the EOD information acquired by the business program 3-1 is accessed. Wait until. In addition, the data end position (EO
Although D) changes, the change of the data end position can be recognized only by the access business program (3-1) that causes the CA division, so immediately after the division is completed, the information of the data end position is transferred to another business program. (3-2) is notified so that it can be understood (according to EOD information 8 in FIG. 3), and control is performed to guarantee the freshness of the data (the access data is the latest updated data). Conventionally, the EOD information is captured at the time of OPEN and the end position of the data set is recognized to
Since the information was updated at CLOSE, it was not possible to notify other business programs of changes in EOD during transaction processing, so business program (3-1)
If the business program (3-2) is not started and the business program (3-2) is restarted, the state of the latest data set after the CA split cannot be reflected in other business programs (3-2), which guarantees the data freshness. I could not do it.

The exclusive control unit 4a ′ is an improved version of the function of the exclusive control unit 4a of the conventional example shown in FIG. 2. It refers to the CI management table 7, and the CA split processing unit 5b of VSAM indicates that the CA split processing is in progress. For example, a notification of start and end) is obtained and exclusive control is executed.

FIG. 4 shows an example of the control flow of the exclusive control unit 4a '. The steps a to e will be described below.

At step a, whether or not the CA that the transaction is trying to access is being used by another transaction is compared with the CA number of the exclusion information (CI management table 7) in FIG. 3 to make a primary determination. Here, if the CA of the transaction is not used by another transaction, all data of the CA may be accessed. However, when the CA is used by another business program, it is secondarily determined in the next step b whether or not another transaction is being used for each CI.

In step c, if another transaction is accessing the CI ahead of the current CI, wait for the end of this access,
Access when finished.

Steps d and e are exclusive processing when the CA division is in progress. In step d, the CA division processing unit 5b of VSAM
If there is a notification that the CA is being split, the CA will
Determine if it is the same as the CA. If No, execute it,
If Yes, the process returns to step d and waits until the CA division process is completed. Execution starts when the CA split processing is completed. More specifically, what is notified from the CA division processing unit 5b at the time of CA division is a division start notification and division completion notification, and based on these, the "CA division in progress" determination is performed.

In other words, the CA is being divided means that the division process has been started and the division completion notification has not yet been issued.

Further, during the CA division, each access is waited until the division is completed and the access is executed after the division is completed by the notification information at the time of the division start and the division completion.

FIG. 5 shows two exclusive control examples to which the present embodiment is applied. The left side of the figure shows two business programs APL
1, APL2 CI access request content, the right side shows the exclusive control result. In the example of FIG. 3A, CI2 is the same as APL1 and APL2.
Is included, CI2 of APL2 is executed after the access of CI2 of the preceding APL1 is completed. CI1 is APL1 in the example of FIG.
And APL2 are commonly used. in this case,
Which of APL1 and APL2 precedes access to CI1 depends on the acceptance timing of each transaction of APL1 and APL2, the access order of CI1 within each APL transaction, and the like.

In order to know which of APL1 and APL2 is using CI1 first, for example, when APL2 accesses CI1, it is necessary to determine whether or not the transaction (APL1) other than itself uses the same CI. good. If there is another transaction (APL1) that is accessing CI1, this transaction (APL1) waits until this transaction ends access to CI1 and the exclusion is released. As a result, in APL2,
You are accessing CI1 when you have completed access to CI3
It is sufficient to wait for the end of CI1 access of the APL1 transaction, and parallel access is realized.

Next, exclusive control when CA division occurs while APL1 and APL2 are accessing the same CA1 will be described.

For example, assume that APL1 is accessing CI1 while APL2 is accessing CI3. If a CA split occurs at this time and a new CA is to be cut out, either: -Records cannot be stored in CA1 due to the addition of records in CI1 or-Records cannot be stored in CA1 due to the addition of records in CI3. is there.

At this point, the storage area is insufficient with CA1 alone, so CA splitting occurs and the storage area for CA2 is secured. In this case, the “judgment during CA division” is made in d of FIG. 4, and if the CA division is in progress, the access of the CA is waited until the CA division is completed, and the EOD information is reflected when the division is completed. Then, control is performed so that the CI access is executed thereafter (the bottom step in FIG. 4). The following is an example when CA split occurs due to the extension when adding the CI3 record of APL2.

a) Exclusive information in CI1 access of APL1 is CA1 + CI1 and only this APL1 holding this exclusive information can access this location. Even if APL2 tries to access CI1, it waits due to the exclusive information of APL1 which is another transaction.

b) When a division occurs due to the addition of data in CI3 of APL2, APL2 holds exclusive information of CA1 + CI3, then accesses CI3, and a new CI7 of CA2 is generated by this extension. The period during which the CA2 is secured is the access inhibition period. After that, the data is stored in CI7 of CA2 (CI1 in the relative CI number in CA2). As a result, the exclusive information of APL2 is CA1 + CI3 and CA2 + CI7.
Becomes APL1 tries to access CI1 but waits for the suppression period during CA split. The suppression information at this time is "CA
It is information of "1", "CA2" and "splitting".

c) After CA division is completed, EOD information is updated and immediately APL1, APL2
APL1 and APL2 can recognize EOD by notifying CA2 + CI
7 matches.

d) After the CA division is completed, release the access suppression of APL1 and
To access. The exclusive information of APL1 does not need to be changed.

e) APL2 can recognize CI7 based on the notified EOD information, and even during the processing of the same transaction.
You can refer to and update CI7. The APL1 can also access the CI7 by the notification of the EOD information.

Next, changes in EOD recognition of APL1 and APL2 in the above-described processing example are as follows.

Only the data up to CI6 is known in the OPEN processing of APL1. Therefore, EPL information that only data of CI1 to CI6 is present is set in APL1.

Similarly, at the time of OPEN, it recognizes that there is only CI1 to CI6 data.

While accessing APL1, CA1 generated a CA split by adding the record of APL2, and CA2 was created, and CI7 was created.

After APL1 accesses CI1 in the above state, CI7 generated by APL2 has only CI6 as EOD information of APL1.
When PL1 accesses CI7, there is no data.

However, CA split occurs at the trigger of APL2, and when the CI split is completed, the APL1 is notified of the change in the EOD information when the CA split is completed. By reflecting this EOD information in APL1, APL1 can access up to the latest data (that is, up to CI7).

〔The invention's effect〕

As described above, according to the present invention, the access efficiency to shared data from a plurality of online terminals is improved and the response time can be shortened.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the structure of a VSAM data set, FIG. 2 is a structural diagram of a database system for explaining a conventional exclusive control method, and FIG. 3 is a structural diagram of an embodiment system of the present invention, FIG. Is a flow chart of exclusive control, and FIG. 5 is a diagram showing an application example of the present embodiment. In the figure, 3-1 and 3-2 are business programs, 4 is an online processing system AIM, 4a 'is an exclusive control unit, 4b is a transaction analysis unit, 5 is a data management system VSAM, 5a is an exclusive control unit, and 5b. Is a CA division processing unit, 6 is a database, 7
Represents a CI management table.

Claims (1)

[Claims] 1. A plurality of online terminals, a database (6), a first division unit (CI) as a transfer unit of a data set of the database (6), and the first division unit (C).
Data management means (5) that hierarchically manages by a second division unit (CA) at a higher level than I) and performs exclusive control for each first division unit (CI), and a transaction input from an online terminal. The online processing means (4) is provided with an online processing means (4) for analyzing and controlling access to the shared data set of the database (6).
Normally performs exclusive control of the shared data set in the second division unit (CA) accessed by the transaction and in the first division unit (CI) among them, and the data management means ( 5) the first division within the second division unit (CA) only while the division division processing is being performed on the second division unit (CA).
The access to the division unit (CI) is the second division unit (C
An exclusive control method for shared data sets, which is characterized by exclusive control in A).