Method and apparatus for chunk based transaction logging with asynchronous input/output for a database management system

• US 20030009477A1
• Filed: 06/15/2001
• Published: 01/09/2003
• Est. Priority Date: 06/15/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wilding, Mark Francis, Zheng, Roger Luo Quan
• Granted Patent: US 6,813,623 B2
• Time in Patent Office: Days
• US Class Current: 707/104.1
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27

Abstract

A method and apparatus are provided for storing transaction data for a plurality of database applications in a multiple access database management system having permanent storage and a transaction log buffer to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said applications are used to store data in said transaction log buffer, including granting exclusive write access reservations in said transaction log buffer to a plurality of said database connection agents; and allowing database connection agents to write transaction data records to previously granted write access reservations while granting exclusive access reservations to other database connection agents.

Claims

1. A method of storing transaction data for a plurality of database applications in a multiple access database management system having permanent storage and a transaction log buffer to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said applications are used to store data in said transaction log buffer, comprising:

granting exclusive write access reservations in said transaction log buffer to a plurality of said database connection agents; and

,

allowing database connection agents to write transaction data records to previously granted write access reservations while granting exclusive access reservations to other database connection agents.

2. The method of claim 1, comprising:

granting an exclusive write access reservation in said transaction log buffer to a database connection agent;

granting an exclusive write access reservation in said transaction log buffer to another database connection agent;

while allowing said previous database connection agent to write a data record to its respective write access reservation in said transaction log buffer.

3. The method of claim 2 comprising:

granting an exclusive write access reservation in said transaction log buffer to a database connection agent;

granting an exclusive write access reservation in said transaction log buffer to another database connection agent for contiguous reservation in said transaction log buffer;

while allowing said previous database connection agent to write a data record to its respective write access reservation in said transaction log buffer.

4. The method of claim 1 comprising:

sequentially granting write access reservations in said transaction log buffer to database connection agents;

while allowing database connection agents to write data records to previously granted write access reservations in said transaction log buffer.

5. The method of claim 4 comprising:

sequentially granting contiguous write access reservations in said transaction log buffer to database connection agents;

while allowing database connection agents to write data records independently of and concurrently with other database connection agents to previously granted write access reservations in said transaction log buffer.

6. The method of claim 4, comprising:

dividing said transaction log buffer into a multiplicity of contiguous logical sections of a predetermined size;

sequentially granting contiguous write access reservations in said logical sections of said transaction log buffer to database connection agents;

while allowing other database connection agents to write data records concurrently to previously granted write access reservations in said transaction log buffer.

7. The method of claim 6 wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, and a logger is used to copy data from said transaction log buffer to said permanent storage, said transaction log buffer being divided in a plurality of logical sections of predetermined equal size;

comprising;

while allowing database connection agents to write data records independently and concurrently to previously granted write access reservations in said transaction log buffer;

sequentially granting contiguous write access reservations in a said logical section of said transaction log buffer to database connection agents until said reservations fill said logical section; and

in turn sequentially granting contiguous write access reservations in a next logical section of said transaction log buffer.

8. The method of claim 7 in which reservations of sufficient size may be established straddling adjacent logical sections.

9. The method of claim 6 comprising:

while allowing database connection agents to write data records asynchronously to previously granted write access reservations if any in said transaction log buffer;

sequentially granting contiguous write access reservations in a said logical section of said transaction log buffer to database connection agents until said reservations fill said logical section; and

in turn sequentially granting continguous write access reservations in a next logical section of said transaction log buffer;

determining if all reservations in a logical section have been filled with data records,

copying transaction data records from a data filled logical section to said permanent storage; and

,

subsequently making said data filled logical section available for data storage.

10. The method of claim 9 for storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage, and a transaction log buffer divided into a multiplicity of logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, and a logger is used to copy data from said transaction log buffer to said permanent storage, comprising:

allowing database connection agents to write data records asynchronously to any previously granted write access reservations in said transaction log buffer;

sequentially granting contiguous write access reservations in a said logical section of said transaction log buffer to database connection agents until said reservations fill said logical section; and

in turn sequentially granting continguous write access reservations in a next logical section of said transaction log buffer;

counting the number of reservations made in a logical section and counting the number of reservations in said logical section that have been filled with data records

comparing the number of reservations made in a logical section with the number of reservations filled with data in said logical section;

when the number of reservations made and the number of reservations filled are equal marking said logical section as a filled logical section;

allowing data records from said filled logical section to be copied to permanent storage;

copying transaction data records from said data filled logical section to said permanent storage;

determining when all data records from said filled logical section have been copied to permanent storage;

making said data filled logical section available for data storage when all data records from said data filled logical section have been copied to permanent storage.

11. The method of claim 10, comprising:

using said logger to copy data records from said data filled logical section to said permanent storage; and

,

marking said data filled logical section available for data storage after said logger has completed copying data records from said data filled logical section.

12. The method of claim 10 comprising:

counting the number of reservations made in each logical section and counting the number of reservations in said logical section that have been filled with data records,

comparing the number of reservations made with the number of reservations that have been filled with data within each said logical section;

when the number of reservations made and the number of reservations filled within a logical section are equal marking said logical section as a filled logical section;

allowing data records from any filled logical sections to be copied to permanent storage;

using said logger to copy data records from said data filled logical sections to said permanent storage; and

,

marking said data filled logical sections available for data storage after said logger has completed writing data records from said data filled logical sections to permanent storage

14. The method of claim 13 comprising:

sequentially granting contiguous write access reservations in said transaction log buffer to database connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer by;

a) granting control of said buffer latch at an initial position in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding the latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

releasing said control of said latch from said database connection agent;

e) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

f) repeating steps a to e, and

allowing any database connection agents to copy predetermined transaction data records into their respective data reservations even while control of said buffer latch is under control of any other database connection agent.

15. The method of claim 14, comprising:

sequentially granting contiguous write access reservations in said transaction log buffer to database connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer by;

a) granting control of said buffer latch at an initial position in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding said latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

e) releasing said control of said latch from said database connection agent;

g) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

g) repeating steps a to f, and

allowing any database connection agents to copy predetermined transaction data records into their respective data reservations even while control of said buffer latch is under control of any other database connection agent.

16. The method of claim 15 for storing transaction data for a multiplicity of database applications in a multiple access database management system wherein said database management system has permanent storage, a transaction log buffer divided into a multiplicity of logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, a latch for said buffer, and a logical section counter associated with each said logical section, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, said method comprising:

sequentially granting contiguous write access reservations in a logical section of said transaction log buffer to database connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer by;

a) granting control of said buffer latch at an initial position of a logical section in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding said latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

e) incrementing said logical buffer offset by a predetermined amount from an initial value

f) releasing said control of said latch from said database connection agent;

g) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

h) repeating steps a to g until said logical section has been filled with reservations,

allowing any database connection agents to copy predetermined transaction data records into their corresponding data reservations in said logical section even while control of said buffer latch is under control of any other database connection agent, and

decrementing said logical section counter when data has been stored in a data reservation, marking said logical section as full when said counter returns to said initial count, and allowing all transaction data within said logical section to be copied to permanent storage.

17. The method of claim 16 for storing transaction data for a multiplicity of database applications in a multiple access database management system having:

permanent storage, a transaction log buffer divided into a multiplicity of contiguous logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, a latch for said buffer, and a logical section counter associated with each said logical section, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, said method comprising;

sequentially granting contiguous write access reservations in a logical section of said transaction log buffer to connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer by;

a) granting control of said buffer latch at an initial position of a logical section in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding the latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

e) incrementing said logical section counter by a predetermined amount from an initial count

f) releasing said control of said latch from said database connection agent;

g) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

h) repeating steps a to g until said logical section has been filled with reservations,

i) allowing any database connection agents to copy predetermined transaction data records into their respective data reservations in said logical section even while control of said buffer latch is under control of any other database connection agent, and

j) decrementing said logical section counter when data has been stored in a data reservation,

k) repeating steps a to j for another logical section available for data storage;

marking a logical section as full logical section when its logical section counter returns to its initial count, and allowing all transaction data within a full logical section to be copied to permanent storage.

18. The method of claim 17 wherein said another logical section is contiguous with an immediately preceding logical section.

19. The method of claim 17 wherein a full logical section is marked as available for data storage for connection agents when all transaction data within said full logical section has been copied to permanent storage.

20. The method of claim 17 wherein said another logical section is not contiguous with an immediately preceding logical section.

21. The method of claim 17 in which a logger connection agent is used to copy data asynchronously to said permanent storage, and a pointer is associated with said permanent storage, said method comprising:

l) using said logger connection agent to copy all transaction data from a full logical section to said permanent storage at a position indicated by said pointer;

m) advancing said pointer to the end of transaction data so copied;

n) marking said full logical section from which all transaction data has been copied as available for data storage;

repeating steps 1 to n for another full logical section.

22. The method of claim 18 in which a logger connection agent is used to copy data asynchronously to said permanent storage, and a pointer is associated with said permanent storage, said method comprising:

l) using said logger connection agent to copy all transaction data from a full logical section to said permanent storage at a position indicated by said pointer;

m) advancing said pointer to the end of transaction data so copied;

n) marking said full logical section from which all transaction data has been copied as available for data storage;

repeating steps 1 to n for another full logical section.

23. The method of claim 19 in which a logger connection agent is used to copy data asynchronously to said permanent storage, and a pointer is associated with said permanent storage, said method comprising:

l) using said logger connection agent to copy all transaction data from a full logical section to said permanent storage at a position indicated by said pointer;

m) advancing said pointer to the end of transaction data so copied;

n) marking said full logical section from which all transaction data has been copied as available for data storage;

repeating steps 1 to n for another full logical section.

24. The method of claim 20 in which a logger connection agent is used to copy data asynchronously to said permanent storage, and a pointer is associated with said permanent storage, said method comprising:

l) using said logger connection agent to copy all transaction data from a full logical section to said permanent storage at a position indicated by said pointer;

m) advancing said pointer to the end of transaction data so copied;

n) marking said full logical section from which all transaction data has been copied as available for data storage;

repeating steps 1 to n for another full logical section.

25. The method of claim 17 in which reservations may be established straddling contiguous logical sections tracking said reservations and the filling thereof by counters in all of the logical sections containing said straddling reservations.

26. The method of claim 1 for storing transaction data for a multiplicity of applications in a multiple access database management system having permanent storage and a transaction log buffer to temporarily store data for said applications before transferring said data to said permanent storage, wherein database connection agents associated with said applications are used to store data in said transaction log buffer, and a logger is used to copy data from said transaction log buffer to said permanent storage, comprising:

dividing said transaction log buffer into a multiplicity of logical sections of predetermined size;

sequentially granting contiguous write access reservations in said logical sections of said transaction log buffer to database connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer.

27. The method of claim 13 for storing transaction data in a multiple access database management system having a transaction log buffer into which transaction data of database applications is copied by database connection agents and permanent storage into which transaction data is loaded from said transaction log buffer, comprising:

or a request from a first database connection agent to store predetermined transaction data in said transaction log buffer,

establishing an exclusive write access reservation in said transaction log buffer for said first database connection agent by;

a) determining a data transaction record starting position in said transaction log buffer to store said predetermined transaction data;

b) determining a corresponding amount of storage space in said transaction log buffer to store said predetermined transaction data;

c) determining a transaction data record ending position using said starting position and said amount of storage space;

d) granting exclusive write access of said amount of storage space in said transaction log buffer between said starting position and said ending position to said database connection agent;

repeating steps b to d for establishing another exclusive write access reservation in said transaction log buffer for another database connection agent using said ending position of said write access reservation of said first database connection agent as a starting position for said another exclusive write access reservation, without waiting for said predetermined transaction data of said first database connection agent to be stored in said established write access reservation of said first database connection agent, and;

storing predetermined transaction data of any database connection agent in the respective established reservation of said database connection agent for said predetermined transaction data.

29. The apparatus of claim 28 for storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage, and a transaction log buffer divided into a multiplicity of logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, and a logger is used to copy data from said transaction log buffer to said permanent storage, comprising:

means for allowing database connection agents to write data records asynchronously to any previously granted write access reservations in said transaction log buffer;

means for sequentially granting contiguous write access reservations in a said logical section of said transaction log buffer to database connection agents until said reservations fill said logical section; and

in turn sequentially granting continguous write access reservations in a next logical section of said transaction log buffer;

means for counting the number of reservations made in a logical section and counting the number of reservations in said logical section that have been filled with data records;

means for comparing the number of reservations made in a logical section with the number of reservations filled with data in said logical section;

means for marking aid logical section as a filled logical section When the number of reservations made and the number of reservations filled are equal;

means for allowing data records from said filled logical section to be copied to permanent storage;

means for copying transaction data records from said data filled logical section to said permanent storage;

means for determining when all data records from said filled logical section have been copied to permanent storage;

means for making said data filled logical section available for data storage when all data records from said data filled logical section have been copied to permanent storage.

30. The apparatus of claim 29 for storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage and a transaction log buffer, having a buffer latch to ensure exclusive access for establishing reservations, said transaction log buffer being adapted to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, comprising:

means for granting control of said buffer latch at a first position in said transaction log buffer to a first database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer;

means for determining the size of said data record;

means for updating the position of said log buffer offset while holding the buffer latch to a second position to define a first data reservation in said transaction log buffer between said first and second positions corresponding to the size of said data record;

means for granting exclusive write access to said first data reservation to said first database connection agent;

means for releasing said control of said latch from said first database connection agent;

means for granting control of said buffer latch at said second position in said transaction log buffer to a second database connection agent; and

means for allowing said first database connection agent to copy said predetermined transaction data record into said first data reservation.

31. The apparatus of claim 30 for storing transaction data for a multiplicity of database applications in a multiple access database management system having:

permanent storage, a transaction log buffer divided into a multiplicity of contiguous logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, a latch for said buffer, and a logical section counter associated with each said logical section, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, said method comprising;

means for sequentially granting contiguous write access reservations in a logical section of said transaction log buffer to connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer including means for;

a) granting control of said buffer latch at an initial position of a logical section in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding the latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

e) incrementing said logical section counter by a predetermined amount from an initial count

f) releasing said control of said latch from said database connection agent;

g) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

h) repeating steps a to g until said logical section has been filled with reservations,

i) allowing any database connection agents to copy predetermined transaction data records into their respective data reservations in said logical section even while control of said buffer latch is under control of any other database connection agent, and

j) decrementing said logical section counter when data has been stored in a data reservation,

k) repeating steps a to j for another logical section available for data storage;

marking a logical section as full logical section when its logical section counter returns to its initial count, and allowing all transaction data within a full logical section to be copied to permanent storage.

32. The apparatus of claim 31 for storing transaction data in a multiple access database management system having a transaction log buffer into which transaction data of database applications is copied by database connection agents and permanent storage into which transaction data is loaded from said transaction log buffer, comprising:

means for establishing an exclusive write access reservation in said transaction log buffer for a first database connection agent for a request from said first database connection agent to store predetermined transaction data in said transaction log buffer, by;

a) determining a data transaction record starting position in said transaction log buffer to store said predetermined transaction data;

b) determining a corresponding amount of storage space in said transaction log buffer to store said predetermined transaction data;

c) determining a transaction data record ending position using said starting position and said amount of storage space;

d) granting exclusive write access of said amount of storage space in said transaction log buffer between said starting position and said ending position to said database connection agent;

repeating steps b to d for establishing another exclusive write access reservation in said transaction log buffer for another database connection agent using said ending position of said write access reservation of said first database connection agent as a starting position for said another exclusive write access reservation, without waiting for said predetermined transaction data of said first database connection agent to be stored in said established write access reservation of said first database connection agent, and;

storing predetermined transaction data of any database connection agent in the respective established reservation of said database connection agent for said predetermined transaction data.

38. A computer program product adaptable for embodiment on a computer readable signal-bearing medium comprising computer program code means adapted to perform all the steps of claims 1, 10, or 17 when said program is run on a computer.

13. A method of storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage and a transaction log buffer, having a buffer latch to ensure exclusive access for establishing reservations, said transaction log buffer being adapted to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, comprising:

granting control of said buffer latch at a first position in said transaction log buffer to a first database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer;

determining the size of said data record;

updating the position of said log buffer offset while holding the buffer latch to a second position to define a first data reservation in said transaction log buffer between said first and second positions corresponding to the size of said data record;

granting exclusive write access to said first data reservation to said first database connection agent;

releasing said control of said latch from said first database connection agent;

granting control of said buffer latch at said second position in said transaction log buffer to a second database connection agent;

allowing said first database connection agent to copy said predetermined transaction data record into said first data reservation.

28. Apparatus for storing transaction data for a plurality of database applications in a multiple access database management system having permanent storage and a transaction log buffer to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said applications are used to store data in said transaction log buffer, comprising:

means for granting exclusive write access reservations in said transaction log buffer to a plurality of said database connection agents; and

,

means for allowing database connection agents to write transaction data records to previously granted write access reservations while granting exclusive access reservations to other database connection agents.

33. An article comprising:

a computer-readable signal bearing medium wherein said medium is a recordable data storage medium or a modulated carrier signal;

means in the medium for storing transaction data for a plurality of database applications in a multiple access database management system having permanent storage and a transaction log buffer to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said applications are used to store data in said transaction log buffer, comprising;

means for granting exclusive write access reservations in said transaction log buffer to a plurality of said database connection agents; and

,

means for allowing database connection agents to write transaction data records to previously granted write access reservations while granting exclusive access reservations to other database connection agents.

34. The article of claim 33 for storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage, and a transaction log buffer divided into a multiplicity of logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, and a logger is used to copy data from said transaction log buffer to said permanent storage, comprising:

means for allowing database connection agents to write data records asynchronously to any previously granted write access reservations in said transaction log buffer;

means for sequentially granting contiguous write access reservations in a said logical section of said transaction log buffer to database connection agents until said reservations fill said logical section; and

in turn sequentially granting continguous write access reservations in a next logical section of said transaction log buffer;

means for counting the number of reservations made in a logical section and counting the number of reservations in said logical section that have been filled with data records

means for comparing the number of reservations made in a logical section with the number of reservations filled with data in said logical section;

means for marking said logical section as a filled logical section When the number of reservations made and the number of reservations filled are equal;

means for allowing data records from said filled logical section to be copied to permanent storage;

means for copying transaction data records from said data filled logical section to said permanent storage;

means for determining when all data records from said filled logical section have been copied to permanent storage;

means for making said data filled logical section available for data storage when all data records from said data filled logical section have been copied to permanent storage.

35. The article of claim 34 for storing transaction data for a multiplicity of database applications in a multiple access database management system having permanent storage and a transaction log buffer, having a buffer latch to ensure exclusive access for establishing reservations, said transaction log buffer being adapted to store data for said database applications before transferring said data to said permanent storage, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, comprising:

means for granting control of said buffer latch at a first position in said transaction log buffer to a first database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer;

means for determining the size of said data record;

means for updating the position of said log buffer offset while holding the buffer latch to a second position to define a first data reservation in said transaction log buffer between said first and second positions corresponding to the size of said data record;

means for granting exclusive write access to said first data reservation to said first database connection agent;

means for releasing said control of said latch from said first database connection agent;

means for granting control of said buffer latch at said second position in said transaction log buffer to a second database connection agent;

means for allowing said first database connection agent to copy said predetermined transaction data record into said first data reservation.

36. The article of claim 35 for storing transaction data for a multiplicity of database applications in a multiple access database management system having:

permanent storage, a transaction log buffer divided into a multiplicity of contiguous logical sections of predetermined equal size, to temporarily store data for said database applications before transferring said data to said permanent storage, a latch for said buffer, and a logical section counter associated with each said logical section, wherein database connection agents associated with said database applications are used to store data in said transaction log buffer, said method comprising;

means for sequentially granting contiguous write access reservations in a logical section of said transaction log buffer to connection agents;

while allowing database connection agents to write data records asynchronously to previously granted write access reservations in said transaction log buffer including means for;

a) granting control of said buffer latch at an initial position of a logical section in said transaction log buffer to a database connection agent requesting write access to write a predetermined transaction data record to said transaction buffer to define a beginning position of a data reservation for writing;

b) determining the size of said data record of said database connection agent;

c) updating the position of said log buffer offset while holding the latch to an end position for writing to define i) a data reservation for said database applications in said transaction log buffer between said beginning and end positions corresponding to the size of said data record, and ii) an initial position for writing a next data reservation;

d) granting exclusive write access to said data reservation to said database connection agent;

e) incrementing said logical section counter by a predetermined amount from an initial count

f) releasing said control of said latch from said database connection agent;

g) granting control of said buffer latch to another database connection agent at said initial position for writing a next data reservation in said transaction log buffer;

h) repeating steps a to g until said logical section has been filled with reservations,

i) allowing any database connection agents to copy predetermined transaction data records into their respective data reservations in said logical section even while control of said buffer latch is under control of any other database connection agent, and

j) decrementing said logical section counter when data has been stored in a data reservation,

k) repeating steps a to j for another logical section available for data storage;

marking a logical section as full logical section when its logical section counter returns to its initial count, and allowing all transaction data within a full logical section to be copied to permanent storage.

37. The article of claim 36 for storing transaction data in a multiple access database management system having a transaction log buffer into which transaction data of database applications is copied by database connection agents and permanent storage into which transaction data is loaded from said transaction log buffer, comprising:

means for establishing an exclusive write access reservation in said transaction log buffer for a first database connection agent for a request from said first database connection agent to store predetermined transaction data in said transaction log buffer, by;

a) determining a data transaction record starting position in said transaction log buffer to store said predetermined transaction data;

b) determining a corresponding amount of storage space in said transaction log buffer to store said predetermined transaction data;

c) determining a transaction data record ending position using said starting position and said amount of storage space;

d) granting exclusive write access of said amount of storage space in said transaction log buffer between said starting position and said ending position to said database connection agent;

repeating steps b to d for establishing another exclusive write access reservation in said transaction log buffer for another database connection agent using said ending position of said write access reservation of said first database connection agent as a starting position for said another exclusive write access reservation, without waiting for said predetermined transaction data of said first database connection agent to be stored in said established write access reservation of said first database connection agent, and;

storing predetermined transaction data of any database connection agent in the respective established reservation of said database connection agent for said predetermined transaction data.