Tag: Linux

  • Scaling up Cardinality Estimates in 12.1.0.2

    Scaling up Cardinality Estimates in 12.1.0.2

    Scaling up Cardinality Estimates in 12.1.0.2 Topic: Counting the number of distinct values (NDV) for a table column has important applications in the database domain, ranging from query optimization to optimizing reports for large data warehouses. However the legacy SQL method of using SELECT COUNT (DISTINCT <COL>) can be very slow. This is a well

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  • Flame Graphs for Oracle

    Flame Graphs for Oracle

    Flame Graphs for Oracle Topic: This post is a hands-on introduction to using on-CPU Flame Graphs for investigating Oracle workloads. This technique is about collecting and visualizing sampled stack trace data to analyze and troubleshoot Oracle processes at the OS level (in particular applied to Linux). Motivations: The techniques and tools described here can be

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  • A Closer Look at CALIBRATE_IO

    A Closer Look at CALIBRATE_IO

    A Closer Look at CALIBRATE_IO Topic: This blog entry is about investigating Oracle’s DBMS_RESOURCE_MANAGER.CALIBRATE_IO Spoiler: For quantitative analysis of storage performance and in particular for measuring random read I/O in Oracle, I’d rather advise the use tools that allow generating test workloads in a controlled manner, in a way that can be understood and measured

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