JPH01205351A - Locking control system - Google Patents

Abstract

PURPOSE:To minimize cost required for lock by executing update when an access is accompanied with the update of data and abbreviating the check of lock at the time of access except for the above case. CONSTITUTION:When there is an access request from a transaction, a buffer control means 2 checks whether a data block concerned exists or not in a buffer group corresponding to the transaction. If it does not exist, a lock calling means 5 is started, and the data block is loaded. If it exists, a control information read means 3 reads access control information of a buffer concerned from an access control information storage means 1. When information is read furthermore, access control information is a collation lock, and the access request at that time is accompanied with update, the means 5 is started, but the processing terminates without starting the means 5 except for the above case.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lock control method, particularly to a lock control method for a database management system for multiple transactions.

[Conventional technology]

Conventionally, this type of lock control method calls a locking means whenever a transaction requests access to data, and the locking means first locks the data, that is, prevents the transaction from accessing or updating the data. It is checked whether the access request is prohibited or not, and if the access request is not locked, an update lock is performed if the access request is a reference, and a reference and update lock is performed if the access request is an update.

[Invention or problem to be solved]

The above-described conventional lock control method has the disadvantage that lock processing is performed even when the same data is accessed for the second time or later within a transaction, so that processing is performed on data that has already been locked, resulting in poor efficiency.

Means for Solving the Problems] The lock control method of the present invention is a lock control method in a database management system for multiple transactions. An access management information storage means for storing management information is provided for each transaction, the access management information is initialized at the start and end of a transaction, and data on the buffer is stored within the transaction. When there is an access for the first time, the corresponding lock is performed and the corresponding access management information is updated, and when accessing the same data for the second time or later within a transaction, the access management + ft information is referred to and the result is updated as described above. When the access is a reference lock and the access involves updating data, the update lock and the access management information are updated to the update lock, but for other accesses, the lock check by the lock means is omitted. It is characterized by the following.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing the configuration of the present invention, in which access management information storage means 1. Buffer control means 2゜management information successive output means 3. Management information writing means 4. It consists of lock calling means 5 and locking means 6.

Some database management systems for a plurality of transactions provide a buffer group for each transaction, and use necessary data by loading it from a database in blocks. The access management information storage means 1 stores access management information for such a buffer, that is, information indicating whether the data on the buffer is reference-locked or updated, and is used to store access management information for such a buffer. Set to initial value at start and end. Here,
A reference lock means that it can be referenced by other transactions but not updated, and an update lock means that it is not allowed to be referenced or updated by other transactions.

When there is an access request from a transaction, the buffer control means 2 checks whether the corresponding data block exists in the buffer group corresponding to the transaction, and if there is not, activates the lock calling means 5 and then accesses the data block. The data block is loaded, and if there is, the access management information of the corresponding buffer is read out by the management information reading means 3 from the access management information storage means 1. Further, if the read access management information is a reference lock and the access request at that time involves an update, the lock calling means 5 is activated, but in other cases, the lock calling means 5 is activated. The processing is completed without activating the means 5.

The management information reading means 3 reads the access management information from the access management information storage means 1 under the control of the buffer control means 2 using the buffer number as a key, and the management information writing means 4 reads the access management information from the access management information storage means 1 at the start and end of a transaction. When initial value writing is activated by the lock calling means 5, the access management information for the designated buffer number is updated.

Next, the operation of this embodiment will be explained according to the flowchart shown in FIG.

First, when there is an access request to data, the buffer control means 2 searches the buffer corresponding to the transaction and checks whether it exists on the buffer (
Step ■). If data exists on the buffer, that data is used and the access management information successive means 3 is used to refer to the access management information. As a result of the reference, if the access management information is a reference lock, it is checked whether the access request at that time involves an update (step (2)).

If YES, the lock discharging means 5 is called (step 2), the locking means 6 is locked (step 2), and the management information writing means 4 is updated to the update lock of the access management information (step 2). ■).

On the other hand, if the result of the investigation in step ■ is NO,
The process ends without further processing. That is, if it is the second or later access within a transaction, the activation of the lock calling means 5 and the process of updating the access management information are not performed.

Next, if the result of the investigation in step ■ is No,
Since the access request is the first access within the transaction, the lock calling means 5 is called (step 2), the locking means 6 locks the data (step 2), and the management information writing means 4 Update the access management information (step ■)
, load data into the appropriate buffer (stepwise).

〔Effect of the invention〕

As described above, the present invention has the effect of minimizing the cost required for locking by preventing locking of data existing on a buffer from being performed more than once within a transaction.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention, and FIG. 2 is a flowchart showing the processing of the present invention. DESCRIPTION OF SYMBOLS 1... Access management information storage means, 2... Buffer control means, 3... Management information reading means, 4... Management information writing means, 5... Lock calling means, 6... Lock means.

Claims (1)

[Scope of Claims] In a lock control method in a database management system for multiple transactions, an access management information storage for storing access management information indicating the distinction between reference locks and update locks for each buffer into which data is loaded from a database. A means is provided for each transaction, and the access management information is initialized at the start and end of the transaction, and when the data on the buffer is accessed for the first time within the transaction, the corresponding lock is taken. The access management information is updated, and when the same data is accessed for the second time or later within a transaction, the access management information is referred to, and the result is the reference lock, and the access involves updating the data. 2. A lock control method characterized in that when the access management information is accessed, the update lock and the access management information are updated to the update lock, but the lock check by the locking means is omitted during other accesses.