Standby Database Synchronization via Placeholder Redo Records
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Solution Overview
Problem
Standby databases often fail to remain synchronized with primary databases during non-logged workloads, leading to data inconsistency issues when the standby database takes over, due to the high costs and performance problems associated with continuous synchronization.
Innovation Solution
The implementation of placeholder redo records and data block copying, where placeholder redo records are inserted into the redo stream at the primary database, and corresponding data blocks are sent to the standby database, allowing the standby to maintain synchronization even without logging, by applying the data blocks to ensure identical data sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous synchronization is performed using redo logs, then data consistency between primary and standby databases is maintained, but system overhead and performance degradation occur
Solution Approach 1:
The patent extracts only the essential synchronization information (data blocks) from the traditional redo log mechanism. Instead of processing complete redo logs, the system identifies and extracts only the changed data blocks that need to be synchronized to the standby database, reducing the volume of data processed and the associated overhead.
Solution Approach 2:
The synchronization process is segmented into identifying changes, extracting data blocks, and transferring only those specific blocks. This segmentation allows the system to avoid the overhead of processing entire redo logs and instead focus only on the minimal necessary data for maintaining consistency.
2Productivity
If logging is turned off to reduce synchronization overhead, then system performance improves, but the standby database fails to remain synchronized with the primary database
Solution Approach 1:
The patent introduces an intermediary mechanism that operates between the primary and standby databases without requiring full logging. This intermediary identifies changes and facilitates selective data block transmission, enabling synchronization with reduced overhead compared to traditional redo log processing.
3Reliability
If traditional redo log processing is used, then complete data changes are captured, but significant overhead is incurred from redo generation, archiving, and transport
Solution Approach 1:
The patent extracts only the essential synchronization information (data blocks) from the traditional redo log mechanism. Instead of processing complete redo logs, the system identifies and extracts only the changed data blocks that need to be synchronized to the standby database, reducing the volume of data processed and the associated overhead.
Data Source
AI summary
A computer program product, system, and computer implemented method for automatic maintenance of standby databases for non-logged workloads, the process comprising: maintaining a redo stream of redo records sent from a primary database to a standby database, identifying a change made at the primary database for which a redo record was not created, inserting a placeholder redo record into the redo stream corresponding to the change identified at the primary database for which the redo record was not created, sending, to the standby database, a copy of one or more data blocks corresponding to the change that is associated with the placeholder redo record, receiving the placeholder redo record from the redo stream, identifying the copy of the one or more data blocks sent from the primary database corresponding to the placeholder redo record, and applying the copy of one or more data blocks to update the standby database.