Data processing: database and file management or data structures – Database design – Data structure types
Patent
1996-10-25
2000-04-18
Lintz, Paul R.
Data processing: database and file management or data structures
Database design
Data structure types
707201, 39518213, 39518218, 39518502, 395670, 395186, G06F 1730
Patent
active
060526955
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention generally relates to on-line data base processing such as procedures for performing bank deposits and transfers on-line, or procedures for performing airline reservations and ticket issue on-line; and in particular relates to technical improvements for completing such processing of transactions accurately and harmoniously in a cooperative type distributed system such as one in which a plurality of processing devices which are connected together by signal transmission circuits, buses, channels, or the like maintain a database which is divided into sections. The present invention further relates to an improved processing technique, for such an cooperative type distributed system, for making an entry in the log upon transaction commit, for recovery after a failure has occurred, and for referring to the log upon recovery.
BACKGROUND OF THE INVENTION
Processing for performing bank account deposits and transfers on-line may in practice, for example, consist of the sequence of procedures in which request messages are sent from terminals to a host, resources (in the present specification, "resources" is a general term for databases, files, memory tapes or the like) are accessed in the host and are processed, and answer messages are returned from the host to the terminals. These procedures as a whole constitute a single theoretical unit of on-line database processing, and this single theoretical unit is termed a "transaction".
A transaction changes the contents of the resources, but the content of the resources after this change must have a correct meaning from the point of view of the user. For this reason, a transaction must be either committed (completed) or aborted (completely not processed), but must not be left in a part way performed or fragmentary state.
Now, as one possibility for an on-line database processing system, there has been proposed a cooperative type distributed system in which a plurality of processing devices which are connected together by signal transmission circuits maintain a resource which is divided into sections, and cooperate so as to perform distributed processing of transactions. When this cooperative type distributed system is compared with a more usual system in which a single large sized mainframe computer performs centralized processing of the resources, it excels with regard to reduction of cost, dispersal of the risk of failure, and flexibility for increasing or decreasing the size of the system.
However, since with this type of distributed system a single transaction involves resource updating processing by a plurality of processing devices, it is necessary to ensure that the resource updating processing by this plurality of processing devices is consistent; in other words, that the situation does not arise in which, although a certain device has updated a resource with relation to a particular transaction, a different device has not performed such updating. The "two phase commit" method conceived of by N. J. Gray is known as a transaction processing method for this purpose.
With this "two phase commit" method, a transaction is separated into two phases: hypothetical updating and actual updating. When some terminal issues a request for a transaction, this request is received by a single processing device. In the initial hypothetical updating phase, this single processing device which has received the transaction (hereinafter termed the coordinator) inquires from the one or more processing devices (hereinafter termed the participant or devices) which maintain the database or databases to be updated whether such updating is possible or not, and responses are returned from these participants to the coordinator as to whether or not such updating is possible. As a result, the system only proceeds to the actual updating phase in the event that responses have been returned from all of the participants to the effect that such updating is possible. In this actual updating phase, commit commands are issued from the coordinator to all of t
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Abe Ken-ichi
Imafuku Yukiharu
Inoue Toshiyuki
Kirita Hitoshi
Konno Yuichi
Corrielus Jean M.
Lintz Paul R.
NTT Data Communications Systems Corporation
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