Locking mechanism for check in/check out model which maintains data consistency amongst transactions

• US 5,809,503 A
• Filed: 08/26/1996
• Issued: 09/15/1998
• Est. Priority Date: 07/08/1993
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Aoshima, Masaaki
• Primary Examiner(s): Kulik, Paul V.
• Application Number:
  US08/702,858
• Time in Patent Office: 750 Days
• Field of Search: 395/601-617, 395/726, 707/9, 707/8, 707/200, 707/201
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 16/2343 Locking methods, e.g. distributed locking or locking implementation details
• CPC Class Codes: G06F 9/466 Transaction processing
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

A locking mechanism for a check-in/check-out model in which one or a plurality of clients make access to a public database of a server, includes a long transaction management part, provided in the server, for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the client, a short transaction management part, provided in the server, for managing transactions which do not copy data from the public database, and a transaction list storing information indicative of contents of transactions carried out by each of the long transaction management part and the short transaction management part. The long transaction management part waits the check-in of arbitrary data until another transaction making reference to the arbitrary data ends when the other transaction is detected from the transaction list between the check-out and the check-in.

Claims

1. A locking mechanism for a check-in/check-out model in which at least one and a plurality of clients make access to a public database of a server, said locking mechanism comprising:

long transaction management means, provided in the server, for managing copy transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the at least one and a plurality of clients;

short transaction management means, provided in the server, for managing reference transactions which do not copy data from the public database; and

a transaction list storing information indicative of whether transactions carried out by each of said long transaction management means and said short transaction management means include reference and copy transactions,

said long transaction management means including means for waiting the check-in of data until another transaction making reference to the data of the copy ends when said another transaction is detected from said transaction list between the check-out and the check-in.

2. The locking mechanism as claimed in claim 1, wherein said long transaction management means includes means for prohibiting other transactions making reference to the data from being carried out when a waited transaction making reference to the data and generated between the check-out and check-in waits for the check-in of the data until the waited transaction ends.

4. The locking mechanism as claimed in claim 1, wherein said transaction list is provided in the server.

3. A locking mechanism for a check-in/check-out model in which at least one and a plurality of clients make access to a public database of a server, said locking mechanism comprising:

long transaction management means, provided in the server, for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the at least one and a plurality of clients;

short transaction management means, provided in the server, for managing transactions which do not copy data from the public database;

a transaction list storing information indicative of contents of transactions carried out by each of said long transaction management means and said short transaction management means; and

said long transaction management means including means for waiting the check-in of data until another transaction making reference to the data ends when said another transaction is detected from said transaction list between the check-out and the check-in;

wherein said transaction list includes at least an identification number of each transaction, an identification number of each data and status information related to each transaction in correspondence with a renewal mode and a reference mode of each transaction; and

said long transaction management means and said short transaction management means make reference to said transaction list depending on a transaction which is carried out, register information related to the transaction in a portion of said transaction list corresponding to the mode when carrying out the transaction, and delete registered information related to the transaction from said transaction list when the transaction ends.

5. A server having a locking mechanism for a check-in/check-out model in which at least one and a plurality of clients make access to a public database coupled to said server, said server comprising:

long transaction management means for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the at least one and a plurality of clients;

short transaction management means for managing reference transactions which do not copy data from the public database; and

a transaction list storing information indicative of whether transactions carried out by each of said long transaction management means and said short transaction management means include reference and copy transactions,

said long transaction management means including means for waiting the check-in of data until another transaction making reference to the data of the copy ends when said another transaction is detected from said transaction list between the check-out and the check-in.

6. The server as claimed in claim 5, wherein said long transaction management means includes means for prohibiting other transactions making reference to the data from being carried out when a transaction making a reference to the data and generated between the check-out and the check-in waits for the check-in of the data until the waited transaction ends.

7. A locking mechanism for a check-in/check-out model in which at least one and a plurality of clients make access to a public database of a server, said locking mechanism comprising:

long transaction management means, provided in the server, for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the at least one and a plurality of clients;

short transaction management means, provided in the server, for managing transactions which do not copy data from the public database;

a transaction list storing information indicative of contents of transactions carried out by each of said long transaction management means and said short transaction management means; and

said long transaction management means including means for waiting the check-in of data until another transaction making reference to the data ends when said another transaction is detected from said transaction list between the check-out and the check-in;

wherein said server comprising;

long transaction management means for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the at least one and a plurality of clients;

short transaction management means for managing transactions which do not copy data from the public database;

a transaction list storing information indicative of contents of transactions carried out by each of said long transaction management means and said short transaction management means; and

said long transaction management means including means for waiting the check-in of data until another transaction making reference to the data ends when said another transaction is detected from said transaction list between the check-out and the check-in;

said transaction list includes at least an identification number of each transaction, and identification number of each data and status information related to each transaction in correspondence with a renewal mode and a reference mode of each transaction; and

said long transaction management means and said short transaction management means make a reference to said transaction list depending on a transaction which is carried out, register information related to the transaction in a portion of said transaction list corresponding to the mode when carrying out the transaction, and delete registered information related to the transaction from said transaction list when the transaction ends.

8. A locking mechanism for a server containing a public database, comprising:

means for performing a database read operation and database write operation of a data;

a transaction list storing information indicative of the read and write operations; and

means for scheduling said read operation and said write operation of said data with said write operation being scheduled after said read operation ends using said transaction list.

9. A locking mechanism of a server connected with a public database, comprising:

long transaction management means in the server for managing a check-out transaction copying data from the public database followed by a check-in transaction writing data into the public database

a transaction list storing information indicative of the check-out and check-in transactions; and

waiting means for checking said transaction list and, when an intervening transaction is detected between said check-out transaction and said check-in transaction, said check-in transaction being delayed by said waiting means until said intervening transaction terminates.

10. A locking mechanism for a check-in/out model where check-out is a read from a database, and check-in is a write into the database, said locking mechanism comprising:

a transaction management mechanism including a transaction list accepting a single check-in transaction and plurality of check-out transactions for data at a same time, in a way in which the check-out transactions do not overlap or span an updating time period for the data processed responsive to the check-in transaction and all of the check-out transactions are completed before the check-in transaction is allowed to perform the write into the database using the transaction list.

11. A database locking method including copy requests, read requests, write requests and transactions, comprising:

preventing, using a transaction list, an open first transaction that has performed a copy request on data from performing a write request on the data until all second transactions that open subsequent to the first transaction and, which are stored on the transaction list, and which includes read only requests on the data, have closed.

12. A database method, comprising:

opening a first transaction that includes a copy and a write request and storing the first transaction on a transaction list;

opening a second transaction that includes only read requests and storing the second transaction on the transaction list;

allowing the first and second transactions to obtain data from the database;

allowing the first transaction to modify the copied data producing modified data;

preventing the first transaction from writing the modified data into the database if the second transaction is on the transaction list as open; and

allowing the first transaction to write the modified data into the database if the second transaction is off the transaction list as closed.

13. A database method, comprising:

performing mutually exclusive check-in transactions;

making a check-out transaction mutually exclusive with a write of a check-in transaction upon arrival of the write that accesses the same data as the check-out and only during a pendency of the write using a transaction list; and

making the write of the arrived check-in transaction wait until the mutually exclusive check-out transaction ends by providing the write with a lower priority than the check-out transaction on the transaction list.