GB2262632A

GB2262632A - Control of access to data records.

Info

Publication number: GB2262632A
Application number: GB9127446A
Authority: GB
Inventors: Peadar O'flathartha; Joseph Eustace
Original assignee: UKEN
Current assignee: UKEN
Priority date: 1991-12-17
Filing date: 1991-12-27
Publication date: 1993-06-23
Also published as: IE914378A1; BE1003858A6; GB9127446D0

Abstract

- After data from a record in a database is transmitted to a memory circuit (5), only write instructions are disabled (7) so that other processors may access the record (2) to read the data and use it. After processing of the data in the memory circuit (8), read instructions are also disabled (9) and the processed data is written to the record (10). This operation takes only a fraction of a second and immediately afterwards, the read/write controller is directed to enable both read and write instructions (12). <IMAGE>

Description

Control of Access to Data Records" The invention relates to the control of access to data records and in particular to such control where there is shared access.

For intelligent workstations which are networked, the manner in which access to stored data records is controlled is very important, especially because of the increasing processor complexity involving access to a multiplicity of data records.

For example, if read and write instructions to a single data record are disabled (i.e. the record is "locked") because a single workstation is editing data in the record, not only can that record not be viewed or edited by another user, but the record may not be used for the carrying out of process applications for which access is required.

PCT Patent Specification No. WO 91/3024 (Microsoft) describes a method of record locking whereby network traffic is reduced and thus performance is improved. This would also help to reduce record locking time. However, we have found that for relational database systems, record locking may cause some disruption. This is particularly true where there is shared use of processing resources, as described in European Patent Specification No. 147574B (IBM). For resource sharing, data stored at one workstation may be required by a remote workstation, possibly using some of the processing capacity of the first workstation.

The reason for this problem is that data in a record must be transmitted to memory where the processor of the computer system carries out various operations on it, for example, data resulting from updating of work orders. While the data is in memory, the computer system prevents read and write instructions to the record in the storage device to prevent simultaneous editing and use of the record while the record is also being updated.

The invention is directed towards providing a process which minimises disruption caused by locking of records while they are being edited.

According to the invention, there is provided a process for control of access to a data record stored on a fixed disk, the process being carried out by an apparatus comprising a processor connected by an address bus and a data bus to a memory circuit and to the fixed disk, the apparatus also including a read/write controller connected to the data bus, the process comprising the steps of: locating the data record on the fixed disk; transmitting data in the record to the memory circuit; inserting a flag in the header of the record in the fixed disk indicating that data in the record is being edited; directing the read/write controller to disable write instructions to the record, while enabling read instructions to the record; editing the data in the memory circuit; directing the read/write controller to disable read instructions to the record in the fixed disk; writing the edited data in the memory circuit to the record on the fixed disk; re-setting the flag in the header of the record on the fixed disk; and directing the read/write controller to enable both read and write instructions to the record.

The invention will be more clearly understood from the following description of some preferred embodiments thereof given by way of example only with reference to the accompanying drawing which is a flow chart illustrating a process of the invention.

Referring to the drawing, there is illustrated a process of the invention indicated generally by the reference numeral 1 for controlling access to a data record 2 stored on a fixed disk 3. The process is carried out by an apparatus which includes a processor which is connected to both an address bus and to a data bus, the address bus having a read/write controller. The address and data buses connect the processor to a memory circuit and to the fixed disk 3. The fixed disk 3 stores relational databases for project management.

Initially, in step 4 the file server processor locates the record 2 on the fixed disk 3 and transmits a write signal on the data bus to the fixed disk 3 causing writing of the data within the record 2 to the memory circuit. This is indicated by step 5. In step 6, the processor using the data bus writes a flag to the header of the record 2 stored on the fixed disk 3 to indicate to other processors on subsequent accesses to the record, that data within the record is being edited. In step 7, the processor directs the read/write controller to disable write instructions on the data bus for the address of the record 2 However, read instructions#are not disabled and subsequently other users using different processors may access the record 2 using the data bus.This allows users to read the record and view it's contents, however, it may not be transmitted to memory of another processor or edited subsequently. Because the data may be read, other processors may use it's contents to carry out various processes.

In step 8, the processor carries out various processing and more specifically, editing, operations on the data while in memory under the instructions of the user. When this is completed, in step 9 read instructions for the record 2 are disabled. At this stage, both read and write instructions are disabled and the record 2 is effectively "locked" from other processors. Immediately, however, the processor transmits the edited data from the memory circuit to the record 2 in step 10, which operation takes only a fraction of a second. In step 11, the header flag for the record 2 is re-set to it's normal status and in step 12 the processor directs the read/write controller to enable both read and write instructions for the record 2. Thus, the record is only locked for a very short period of time, during which it is highly unlikely that another processor would require access.

Thereafter, the record 2 may be accessed in the normal manner.

It will thus be appreciated that the process allows a large amount of flexibility in the manner in which records may be edited with minimum disruption to other users. A data record is only completely "locked" for a fraction of a second while the edited data is being transmitted to the record. While the data is being edited the file may be continuously viewed and used for process applications. The only possible inconvenience for other users is that they may not also edit the file at the same time. While this may be from time to time inconvenient for the users, it is clearly essential for consistency in the storage of data records.

The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail.

Claims

1. A process for control of access to a data record stored on a fixed disk, the process being carried out by an apparatus comprising a processor connected by an address bus and a data bus to a memory circuit and to the fixed disk, the apparatus also including a read/write controller connected to the data bus, the process comprising the steps of:: locating the data record on the fixed disk; transmitting data in the record to the memory circuit; inserting a flag in the header of the record in the fixed disk indicating that data in the record is being edited; directing the read/write controller to disable write instructions to the record, while enabling read instructions to the record; editing the data in the memory circuit; directing the read/write controller to disable read instructions to the record in the fixed disk; writing the edited data in the memory circuit to the record on the fixed disk; re-setting the flag in the header of the record on the fixed disk; and directing the read/write controller to enable both read and write instructions to the record.

2. A process as claimed in claim 1, wherein the record is part of a relational database stored on the fixed disk.

3. A process substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1. A process for control of access to a data record stored in a relational database on a fixed disk, the process being carried out by an apparatus comprising a processor connected by an address bus and a data bus to a memory circuit and to the fixed disk, the apparatus also including a read/write controller connected to the data bus, the process comprising the steps of: : locating the data record on the fixed disk; transmitting data in the record to the memory circuit; inserting a flag in the header of the record in the fixed disk indicating that data in the record is being edited; directing the read/write controller to disable write instructions to the record, while enabling read instructions to the record; editing the data in the memory circuit; directing the read/write controller to disable read instructions to the record in the fixed disk; writing the edited data in the memory circuit to the record on the fixed disk; re-setting the flag in the header of the record on the fixed disk; and directing the read/write controller to enable both read and write instructions to the record.