Month: October 2023
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Direct Path Read Decision in Oracle: Beyond the Optimizer
The performance issue with an SQL query was resolved by using the /*+ PARALLEL(2) */ hint, reducing execution time from 180-200 seconds to milliseconds. The decision to perform a direct read from disk to memory instead of reading blocks from disk was made by the database engine and is controlled by the hidden “_serial_direct_read” parameter. To force direct path read for SQL statements, the running statement can be used with a parallel hint or by setting table statistics. This solution allows for applying a SQL patch and significantly improves query performance.
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“_gc_policy_minimum” parameter and Dynamic Resource Management in Oracle RAC
The content discusses the concept of remastering in database management, particularly regarding Oracle RAC. It explains how remastering reallocates resources among nodes during changes, which can temporarily disrupt access to data. The innovative “lazy remastering” technique minimizes these disruptions by focusing on critical resources, allowing most processes to continue uninterrupted. In upcoming releases from 19.20 onwards, the default value for “_gc_policy_minimum” will change due to an internal bug. It will be reset to 15000, eliminating the need for manual tuning. DRM attributes are intentionally undocumented and should not be altered without support consultation.
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Oracle Database Patching Tips
Patching your database is crucial for security and performance. Develop a strategy based on your organization’s needs. Regularly schedule routine patches, test thoroughly, and inform stakeholders. Prioritize critical security fixes. Read release notes and consider expert blogs. Apply patches selectively, and consider in-place and out-of-place patching methods. Fleet Patching and Provisioning can scale patch deployment effectively.
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Removing old Oracle Grid and Database Homes #JoelKallmanDay
The post discusses the process of cleaning old Oracle Homes after patching database servers. It advises keeping old homes for 15 days as a precaution, then removing them when comfortable with the new ones. The methods described for removal involve the deinstall command and fleet maintenance using cleanup_software verb.
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How to Patch Database Using Fleet Patching
The content details the process of patching Oracle RAC databases using fleet maintenance. It includes steps for creating a gold image, deploying the image to target databases, and migrating instances to the newly patched Oracle Home. It also discusses post-patching tasks such as updating shell scripts and addressing alert.log messages. Additional steps are provided for RMAN catalog users.
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How to Patch Grid Using Fleet Patching
The content discusses grid patching using fleet maintenance for database servers. It outlines the process of creating a gold image for fleet patching, setting up fleet environment checks, creating a location on Software Library in EMCC, and deploying the gold image to the target cluster. The post also provides tips and advice for a smooth patching process.
Osman’s DBlog 