Technique for log records management in database management system

Patent metadata

Field	Value
Publication number	US-11210281-B2
Application number	US-201916383511-A
Country	US
Kind code	B2
Filing date	Apr 12, 2019
Priority date	Mar 14, 2019
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

Disclosed is a computer program stored in a computer-readable storage medium including encoded commands according to an exemplary embodiment of the present disclosure. When the computer program is executed by one or more processors, the computer program allows the one or more processors to perform a method for managing undo information in a database management system (DBMS). The method may include: forming undo information corresponding to an update request by a first transaction in response to the update request by the first transaction in the database management system (DBMS); determining an undo memory chunk to be allocated to the undo information from an undo memory pool on a memory, the undo memory chunk having a variable size; and maintaining the undo information on a space of the memory by using the determined undo memory chunk.

First claim

What is claimed is:

1. A non-transitory computer readable medium including a computer program including encoded commands, which is configured to cause one or more processors to perform a method for managing undo information in a database management system (DBMS) when the computer program is executed by the one or more processors, wherein the method comprises:
determining an undo memory chunk on a memory to be allocated to undo information generated in response to operations, associated with an update request by a first transaction in the database management system (DBMS) being preformed on one or more blocks, wherein the undo memory chunk has a variable size;
determining to maintain the undo information on a space of the memory by using the determined undo memory chunk;
determining to transfer undo information associated with one or more transactions from the memory to a persistent storage by a predetermined condition; and
storing meta information of the undo information in a memory space, after the determining to transfer the undo information associated with one or more transactions from the memory to the persistent storage by the predetermined condition,
wherein determining the undo memory chunk of the memory to be allocated to the undo information includes determining the size of the undo memory chunk to be allocated to the undo information based at least on information on the number of times the first transaction is allocated an undo memory chunk, and
wherein the predetermined condition includes at least one of
a case where a ratio between the memory space occupied by the allocated undo memory chunk to the memory space or an absolute amount occupied by the allocated undo memory chunk in the memory is higher than a predetermined threshold value, or
a case where the one or more blocks, loaded on the memory in association with the update request by the first transaction, need to be disk-flushed.

2. The non-transitory computer readable medium of claim 1 , wherein the determining of the undo memory chunk to be allocated to the undo information includes determining the size of the undo memory chunk to be allocated to the undo information based on information on the number of times the first transaction is allocated an undo memory chunk, and
the size of a first undo memory chunk allocated to the first transaction is smaller than the size of a second undo memory chunk allocated to the first transaction after the first transaction is allocated the first undo memory chunk.

3. The non-transitory computer readable medium of claim 1 , wherein the determining of the undo memory chunk to be allocated to the undo information includes determining the size of the undo memory chunk to be allocated to the undo information based on at least one of available memory size information in the memory or task amount information associated with the first transaction, and
wherein the task amount information includes quantitative data for the undo information corresponding to the first transaction or quantitative data for undo information corresponding to each of one or more updates included in the first transaction.

4. The non-transitory computer readable medium of claim 1 , wherein a size of a first undo memory chunk allocated to first undo information associated with the first transaction and the size of a second undo memory chunk allocated to second undo information associated with a second transaction different from the first transaction are different.

5. The non-transitory computer readable medium of claim 1 , wherein the method further comprises generating a structure configured to use an identifier of the undo memory chunk and the identifier of the first transaction to allow the undo memory chunk to be retrieved.

6. The non-transitory computer readable medium of claim 1 , wherein the method further comprises generating a first hash structure configured to use as an input key at least one of an identifier (ID) of the undo memory chunk, an identifier (ID) of the first transaction, or an identifier (ID) for the undo information associated with the first transaction, and use a pointer for the undo memory chunk as an entry of an output.

7. The non-transitory computer readable medium of claim 1 , wherein subsequent undo information among a plurality of undo information associated with the first transaction includes a pointer value for pointing an address of an undo memory chunk corresponding to preceding undo information among the plurality of undo information associated with the first transaction.

8. The non-transitory computer readable medium of claim 1 , wherein the method further comprises determining whether to return the undo memory chunk used for retaining the undo information to the memory, after the determining to maintain the undo information in the space of the memory by using the determined undo memory chunk.

9. The non-transitory computer readable medium of claim 8 , wherein the determining whether to return to the memory includes determining whether to return the undo memory chunk to the memory based on whether a predetermined time period for retaining the undo information has elapsed from the time when the transaction is committed.

10. The non-transitory computer readable medium of claim 8 , wherein the determining whether to return to the memory includes
determining whether there are transactions committed before a start point of time of an open cursor of which start time is earliest among open cursors which currently exist, and
determining to return the undo memory chunk used for retaining the undo information associated with the transactions committed before the start time of the open cursor of which start time is earliest among the open cursors which currently exist to the memory, if there are transactions committed before the start time of the open cursor of which start time is earliest among the open cursors which currently exist.

11. The non-transitory computer readable medium of claim 8 , wherein the determining whether to return the used undo memory chunk to the memory is performed by a thread dedicated to undo lifetime management,
wherein the thread dedicated to the undo lifetime management retains list information for transactions which are committed, and
wherein the list information includes information on the point of time when the transactions are committed.

12. The non-transitory computer readable medium of claim 1 , wherein the method further comprises
after the determining to transfer the undo information associated with the one or more transactions from the memory to the persistent storage according to a predetermined condition that a ratio or an absolute amount occupied by the allocated undo memory chunk in the memory is higher than a predetermined threshold value,
performing at least one scheme of a scheme of transferring to the persistent storage undo information with a smaller number of access times for a predetermined time period preferentially over undo information with a larger number of access times, or a scheme of preferentially transferring the undo information associated with a committed transaction to the persistent storage, and
wherein the scheme of preferentially transferring the undo information associated with the committed transaction to the persistent storage includes storing in the persistent storage another undo memory chunk other than an undo memory chunk being currently used among undo memory chunks associated with an active transaction, if a ratio or an absolute amount occupied by the allocated undo memory chunk in the memory is higher than the predetermined threshold value after storing the undo information associated with the committed tr

Assignees

• Tmaxdata Co Ltd

Inventors

• Lee Minho
• Lee Hakyong
• Hwang Chanho
• Park Sang Young
• Kim Tai Kyoung
• Na Jeongho

Classifications

• G06F16/2272 Primary

  Management thereof · CPC title

• G06F16/2358 Primary

  Change logging, detection, and notification (replication G06F16/27) · CPC title

• G06F16/22

  Indexing; Data structures therefor; Storage structures · CPC title

• G06F16/23

  Updating · CPC title

• G06F11/3034

  where the computing system component is a storage system, e.g. DASD based or network based (digital input from or digital output to record carriers G06F3/06; digital recording or reproducing G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097) · CPC title