System and method for improving data recovery performance

• US 5,581,750 A
• Filed: 03/15/1993
• Issued: 12/03/1996
• Est. Priority Date: 03/15/1993
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Teng, James Z., Haderle, Donald J.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): VON BUHR, MARIA N
• Application Number:
  US08/031,791
• Time in Patent Office: 1,359 Days
• Field of Search: 395/600, 395/575, 395/650, 364/DIG. 1, 364/DIG. 2
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system and method are provided for recovering a computerized database. During transaction processing of a database, at least one log range is tracked comprising update transaction log records. The log range has a begin value and an end value. The begin value corresponds to a log RBA location of a first access of the database by an updating transaction. The end value corresponds to a log RBA location at a commit or abort of a last updating transaction. The end value corresponds to a point when the database is designated as being read only (called pseudo open). During recovery of the database, the update transaction log records in the log range are applied to a version of the database stored in non-volatile memory.

Claims

1. In a computerized database system having a central processing unit (CPU), volatile memory, non-volatile memory, a plurality of data stored in at least one database, wherein a plurality of transactions access a database for reading or updating, and for each database access, a transaction record is stored at an offset location in a sequential log, a method for recovering a database, comprising the steps of:

during transaction processing of a database, tracking at least one log range comprising update transaction log records, said log range having a begin value and an end value, said begin value corresponding to a log offset location of a first access of the database only by an updating transaction and said end value corresponding to a log offset location at a commit or abort only of a last updating transaction; and

during recovery of the database, applying the update transaction log records in said log range to a version of the database stored in non-volatile memory.

2. The method of claim 1, further comprising the steps for tracking the log range of:

a) designating each database as a pseudo close database;

b) tracking when an updating transaction accesses a database;

c) for a pseudo close database accessed by an updating transaction, designating the pseudo close database as a pseudo open database and recording a corresponding offset location as the log range begin value;

d) for a pseudo open database not accessed by an updating transaction for a predetermined period, designating the pseudo open database as pseudo close and recording a corresponding offset location as the log range end value; and

e) repeating steps (b) through (d) a plurality of times.

3. The method of claim 2 wherein the predetermined period is based on time.

4. The method of claim 2 wherein the predetermined period is based on the number of records in the log.

5. The method of claim 2 further comprising the steps for tracking when an updating transaction accesses a pseudo open database of:

maintaining a counter of uncommitted transactions updating a database;

incrementing the counter when an updating transaction accesses the database; and

decrementing the counter when the updating transaction is committed or aborted,

wherein when the counter has a value of zero, there are no updating transactions accessing the database.

6. In a computerized database system having a central processing unit (CPU), volatile memory, non-volatile memory, and a plurality of data stored in a plurality of databases, wherein a plurality of transactions access a database for reading or updating, wherein for each database access, a transaction record is stored at an offset location in a sequential log, a method for recovering a database, comprising the steps of:

during transaction processing of a database;

a) designating each database as a pseudo close database;

b) tracking when an updating transaction accesses a database;

c) for a pseudo close database accessed by an updating transaction, designating the pseudo close database as a pseudo open database and recording a corresponding offset location of the sequential log as a log range begin value;

d) maintaining a counter of uncommitted transactions updating a pseudo open database;

e) incrementing the counter when an updating transaction accesses the pseudo open database;

f) decrementing the counter when the updating transaction is committed or aborted, wherein when the counter has a value of zero, there are no updating transactions accessing the database;

g) for a pseudo open database not accessed by an updating transaction for a predetermined period, designating the pseudo open database as a pseudo close database and recording a corresponding offset location of the sequential log as a log range end value; and

h) repeating steps (d) through (g) a plurality of times;

during recovery of the database;

applying update transaction log records between each log range begin value and log range end value to a version of the database stored in non-volatile memory.

7. A computerized system for recovering a database wherein a plurality of transactions access the database for reading or updating, and for each database access, a transaction record is stored at an offset location in a sequential log, said system comprising:

means for designating the database as a pseudo close database;

means for tracking when an updating transaction accesses a database;

means for designating a pseudo close database accessed by an updating transaction as a pseudo open database;

means for recording an open log location only when an updating transaction first accesses a pseudo close database as a log range begin value;

means for designating a pseudo open database not accessed by an updating transaction for a predetermined period as a pseudo close database;

means for recording a close log location only when a last updating transaction commits or aborts as a log range end value; and

means for applying update transaction log records in between said log range begin value and said log range end value to a version of the database stored in non-volatile memory.

8. The system of claim 7 further comprising:

means for maintaining a counter of uncommitted transactions updating a database;

means for incrementing the counter when an updating transaction accesses the database; and

means for decrementing the counter when an updating transaction has been committed or aborted,

wherein when the counter has a value of zero, there are no updating transactions accessing the database.