Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-08-06
2001-12-04
Mizrahi, Diane D. (Department: 2171)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06327597
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the data processing field, and more particularly to a method, memory system, and computer program product for implementing lock based delayed space recycle control.
DESCRIPTION OF THE RELATED ART
Relational database management systems (RDBMS) based on the Structured Query Language (SQL) are known. The basic unit of data in a relational database is the relation. DB2/400 is the DBMS that is integrated into the operating system of the International Business Machines Corp. Application System/400 (AS/400) computer system.
Normally when data is fetched from a structured query language (SQL) table, the user program is getting a copy of the data. Because the data for a large object (LOB) data type, such as a character large object block (CLOB) or double byte character large object (DBCLOB), can be very large, a copy of the field should not be made. Instead a mechanism must be provided to let the user access parts of the large piece of data directly in the database file.
Conventional methods for sharing LOB data must make a copy of the piece of the LOB data and then return addressability to the copy. Updates must be made to a new area inside the table to avoid affecting those existing copies. Also a shadowed page technique might be used. Both of these techniques require code to free the shadow or copy when the last locator is freed. Multiple locators to the same page require that each locator have its own copy, which causes slow performance and takes more memory. Or some kind of system wide use count for a copy or shadow is required.
A need exists for a more efficient and effective method, memory system, and computer program product for determining when to do recycle (or do garbage collection of space) implementing lock based delayed space recycle control.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method, memory system, and computer program product for determining when to do recycle (or do garbage collection of space) implementing lock based delayed space recycle control. Other important objects of the present invention are to provide such method, memory system, and computer program product for implementing lock based delayed space recycle control substantially without negative effects and that overcome many disadvantages of prior art arrangements.
In brief, a method, memory system, and computer program product are provided for implementing lock based delayed space recycle control. The memory space recycle method is used with a memory in a computer system. A data element lock is obtained for a data record in a data block. Then an update on the data record is performed. A waiting to be recycled index for the data block is maintained.
In accordance with features of the invention, the waiting to be recycled index includes a record number, an address of the large object block (LOB) and the length of the LOB space. When the last lock or a LOB data element is released the lock storage is freed.
REFERENCES:
patent: 5452445 (1995-09-01), Hallmark et al.
patent: 6012060 (2000-01-01), Loaiza et al.
patent: 6144970 (2000-11-01), Bonner et al.
(IEEE publication) Parallel implementation of the trie structure by I.W. Chan et al., Dept. of Information Systems of Computer Systems, National University of Singapore, Singapore,, pp. 538-543 (Dec. 1994).*
(IEEE publication) Data compression in brain-like multimedia data bases by Charles Alfred Finnlla, Hughes Aircraft Company, Los Angeles, CA, pp. 158-163 (1993).
McKinley Thomas Owen
Ricard Gary Ross
Rocheleau Richard Miles
International Business Machines - Corporation
Mizrahi Diane D.
Pennington Joan
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