Database Rearrangement via Per-Page Exclusive Control
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Solution Overview
Problem
In databases using the sequentially accessing method (SAM), rearranging processes are typically done offline due to the need for exclusive control of subranges, which disrupts online operations and results in inefficient use of storage space due to unused space areas.
Innovation Solution
A database apparatus that performs rearrangement by exclusively controlling only the source and destination logical pages, allowing online access to other pages during the process, and moves logical records from the rear of a subrange to fill space areas without stopping online applications, thereby minimizing the records to be moved and maintaining online operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire subrange is exclusively controlled for rearrangement, then the rearrangement process can be completed, but the subrange cannot be accessed online during the rearrangement
Solution Approach 1:
The patent divides the subrange into multiple logical pages and performs rearrangement on a per-page basis rather than controlling the entire subrange. This segmentation allows different pages to be accessed independently, enabling online operations to continue on pages not currently being rearranged while maintaining data integrity on the active pages through exclusive control.
Solution Approach 2:
The patent implements dynamic exclusive control that shifts from static entire-subrange control to dynamic per-page control. The exclusive control is applied only to the specific logical page being rearranged at any given moment, allowing the system to adaptively manage access rights and maintain online availability while ensuring data integrity during the rearrangement process.
2Device complexity
If data is stored sequentially from the leading position, then the storage structure is simple, but space areas generated by deleted data remain unused
Solution Approach 1:
The patent performs preliminary detection of space areas before the rearrangement process. By identifying the locations and sizes of unused space areas in advance, the system can plan the rearrangement to fill these gaps, ensuring optimal storage utilization while maintaining the simplicity of sequential storage structure.
Solution Approach 2:
The patent changes the storage arrangement parameters by moving data records to fill previously unused space areas. This involves adjusting the position parameters of logical records while maintaining the sequential access method, thereby improving storage utilization without fundamentally changing the storage structure's simplicity.
3Reliability
If the entire subrange is copied and rearranged, then the rearrangement is completed, but the time required for the process increases
Solution Approach 1:
The patent segments the rearrangement process into smaller units corresponding to individual logical pages rather than processing the entire subrange at once. This reduces the time required for each rearrangement operation and allows overlapping of I/O operations, while still achieving complete rearrangement of the subrange through repeated page-level operations.
Solution Approach 2:
The patent enables continuous useful action by allowing online operations to proceed concurrently with rearrangement operations on different logical pages. The system maintains continuous data access capability while performing rearrangement, eliminating the need to stop all operations during the process and thereby reducing total rearrangement time.
Data Source
AI summary
A logical record of a source logical page is moved to a space area or a deletion area in a destination logical page. The source logical page is sequentially set forward from the logical page immediately before the last stored logical page in a subrange. The destination logical page is sequentially set backward from the leading logical page in the subrange. When a logical record is moved, exclusive control is performed in logical page units only on the source logical page and the destination logical page. The access by online operations is not prohibited on other logical pages not exclusively controlled in the same subrange.