Maintaining database consistency when nearing the end of a database recovery log

• US 9,665,599 B2
• Filed: 06/03/2013
• Issued: 05/30/2017
• Est. Priority Date: 06/03/2013
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Slinger, David W., Lee, Stephanie H., Levish, David L.
• Primary Examiner(s): NGUYEN, THU N
• Application Number:
  US13/908,396
• Publication Number:
  US 20140358878A1
• Time in Patent Office: 1,457 Days
• Field of Search: None
• CPC Class Codes: G06F 16/20 of structured data, e.g. relational data
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27

Abstract

Log records are generated by a computer system and stored in a computer readable storage area for recording changes to database objects responsive to receiving transaction requests, wherein the locators for the log records are of a predetermined maximum size that provides a maximum trackable size limit of the storage area. A computer system estimates an amount of time for the storing of the generated log records to fill the storage area up to the maximum trackable size limit. A computer system sets a soft limit to the storage area that is smaller than the maximum trackable size limit, including setting the soft limit based on the estimated amount of time.

Claims

1. A method for database transaction logging, comprising:

generating log records by a computer system and storing them in a computer readable log record storage area for storing log records, wherein the log records record what changes in respective database objects responsive to respective received transaction requests, and wherein locators for the log records indicate locations of the log records in the log record storage area and each log record is of a predetermined maximum size that provides a maximum trackable size limit of the log record storage area where if there is no more space for log records then database transactions must stop;

estimating, by a computer system, an amount of time for the storing of the generated log records to fill the log record storage area up to the maximum trackable size limit, where the estimating includes determining how much log record space was filled during a sampling time interval when transactions occurred for which log records were generated and were stored in the log record storage area, thereby taking up more space in the log record storage area;

setting, by a computer system, a soft limit to the log record storage area that is smaller than the maximum trackable size limit, including setting the soft limit based on the estimated amount of time,

determining the log records have filled the log record storage area up to the soft limit and at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit;

determining the at least one database transaction request is for a certain kind of database transaction; and

blocking at least execution completion of the at least one database transaction for the database transaction request responsive to the determining the at least one database transaction request is for the certain kind of database transaction and responsive to the determining the log records have filled the log record storage area up to the soft limit and the at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit log records.

2. The method of claim 1, comprising:

detecting that the soft limit has been reached and responsively sending a notification to a transaction requestor.

3. The method of claim 2, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a database transaction request from a requestor once the soft limit has been reached.

4. The method of claim 3, comprising:

receiving a response to the disallowed transaction notification from the requestor, wherein the response indicates a requestor selection between aborting the disallowed transaction and committing the disallowed transaction using database transactions for which log records are already stored and without the database transaction further changing the database.

5. The method of claim 2, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a predetermined kind of database transaction request from a requestor once the soft limit has been reached.

6. The method of claim 3, wherein setting the soft limit that is smaller than the maximum trackable size limit of the log record storage area includes setting a plurality of the soft limits, each one of the plurality depending on at least one of a predetermined name of a database object updated by a transaction request, a predetermined importance of a database object updated by a transaction request, a predetermined application executing a transaction request, a predetermined user running the application, and a predetermined recovery condition.

7. A computer program product for database transaction logging, the computer program product including a non-transitory computer readable storage medium having instructions stored thereon for execution by a computer system, wherein the instructions, when executed by the computer system, cause the computer system to implement a method comprising:

generating log records by a computer system and storing them in a computer readable log record storage area for storing log records, wherein the log records record what changes in respective database objects responsive to respective received transaction requests, and wherein locators for the log records indicate locations of the log records in the log record storage area and each log record is of a predetermined maximum size that provides a maximum trackable size limit of the log record storage area where if there is no more space for log records then database transactions must stop;

estimating, by a computer system, an amount of time for the storing of the generated log records to fill the log record storage area up to the maximum trackable size limit, where the estimating includes determining how much log record space was filled during a sampling time interval when transactions occurred for which log records were generated and were stored in the log record storage area, thereby taking up more space in the log record storage area;

setting, by a computer system, a soft limit to the log record storage area that is smaller than the maximum trackable size limit, including setting the soft limit based on the estimated amount of time,

determining the log records have filled the log record storage area up to the soft limit and at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit;

determining the at least one database transaction request is for a certain kind of database transaction; and

blocking at least execution completion of the at least one database transaction for the database transaction request responsive to the determining the at least one database transaction request is for the certain kind of database transaction and responsive to the determining the log records have filled the log record storage area up to the soft limit and the at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit log records.

8. The computer program product of claim 7, wherein the instructions, when executed by the computer system, cause the computer system to implement a method comprising:

detecting that the soft limit has been reached and responsively sending a notification to a requestor.

9. The computer program product of claim 8, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a database transaction request from a requestor once the soft limit has been reached.

10. The computer program product of claim 9, wherein the instructions, when executed by the computer system, cause the computer system to implement a method comprising:

receiving a response to the disallowed transaction notification from the requestor, wherein the response indicates a requestor selection between aborting the disallowed transaction and committing the disallowed transaction using database transactions for which log records are already stored and without the database transaction further changing the database.

11. The computer program product of claim 8, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a predetermined kind of database transaction request from a requestor once the soft limit has been reached.

12. The computer program product of claim 9, wherein setting the soft limit that is smaller than the maximum trackable size limit of the log record storage area includes setting a plurality of the soft limits, each one of the plurality depending on at least one of a predetermined name of a database object updated by a transaction request, a predetermined importance of a database object updated by a transaction request, a predetermined application executing a transaction request, a predetermined user running the application, and a predetermined recovery condition.

14. The system of claim 12, wherein the computer readable storage medium has stored thereon a program for controlling the processor, and wherein the processor is operative with the program to execute the program for:

detecting that the soft limit has been reached and responsively sending a notification to a requestor.

15. The system of claim 14, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a database transaction request from a requestor once the soft limit has been reached.

16. The system of claim 15, wherein the computer readable storage medium has stored thereon a program for controlling the processor, and wherein the processor is operative with the program to execute the program for:

receiving a response to the disallowed transaction notification from the requestor, wherein the response indicates a requestor selection between aborting the disallowed transaction and committing the disallowed transaction using database transactions for which log records are already stored and without the database transaction further changing the database.

17. The system of claim 14, wherein sending the notification to a requestor responsive to detecting that the soft limit has been reached includes sending a disallowed transaction notification to the requestor further responsive to receiving a predetermined kind of database transaction request from a requestor once the soft limit has been reached.

18. The system of claim 15, wherein setting the soft limit that is smaller than the maximum trackable size limit of the log record storage area includes setting a plurality of the soft limits, each one of the plurality depending on at least one of a predetermined name of a database object updated by a transaction request, a predetermined importance of a database object updated by a transaction request, a predetermined application executing a transaction request, a predetermined user running the application, and a predetermined recovery condition.

13. A system for database transaction logging, a comprising:

a processor; and

a computer readable storage medium connected to the processor, wherein the computer readable storage medium has stored thereon a program for controlling the processor, and wherein the processor is operative with the program to execute the program for;

generating log records by a computer system and storing them in a computer readable log record storage area for storing log records, wherein the log records record what changes in respective database objects responsive to respective received transaction requests, and wherein locators for the log records indicate locations of the log records in the log record storage area and each log record is of a predetermined maximum size that provides a maximum trackable size limit of the log record storage area where if there is no more space for log records then database transactions must stop;

estimating, by a computer system, an amount of time for the storing of the generated log records to fill the log record storage area up to the maximum trackable size limit, where the estimating includes determining how much log record space was filled during a sampling time interval when transactions occurred for which log records were generated and were stored in the log record storage area, thereby taking up more space in the log record storage area;

setting, by a computer system, a soft limit to the log record storage area that is smaller than the maximum trackable size limit, including setting the soft limit based on the estimated amount of time,

determining the log records have filled the log record storage area up to the soft limit and at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit;

determining the at least one database transaction request is for a certain kind of database transaction; and

blocking at least execution completion of the at least one database transaction for the database transaction request responsive to the determining the at least one database transaction request is for the certain kind of database transaction and responsive to the determining the log records have filled the log record storage area up to the soft limit and the at least one database transaction request has been received after the log records have filled the log record storage area up to the soft limit log records.