Author: Timur Akhmadeev

Migrating btrfs root partition to ext4 in OVM

Recently I spent some time trying to migrate root partition to another FS type in an OVM environment. The target was to migrate root partition from btrfs to ext4. Here is a short outline of how it was done. 1….

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How to fix the skip scan bug in 18c

A recent Twitter thread had an interesting test case of the optimizer choosing sub-optimal skip scan over range scan. I’ve checked what’s going on, and it happens to be a known bug. Here’s a slightly simplified test case: We have…

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Inefficient queries to ALL_SYNONYMS

Short summary: Queries to ALL_SYNONYMS cause FTS of SYS.OBJ$ which can’t be avoided.

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EBS 12.2 issues seen in the wild

Recently, I was involved in an EBS upgrade project, and also in operational support of an EBS production environment. Based on this project, here is an unsorted list of issues I’ve seen in or around the EBS core. EBS architecture…

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High system time on Windows running in a VM

Recently I’ve seen an issue with CPU usage on a server running Windows 2003 Server in a VMware. This is a small Virtual Machine with just 2 cores allocated (which are possibly mapped to “threads” on a host level but…

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A Simple Way to Monitor Java in Linux

A quick and easy way to know what is it inside Java process that is using your CPU. Using just Linux command line tools and JDK supplied command line utilities.

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Statistics gathering and SQL Tuning Advisor

Our monitoring software found a long running job on one of our client’s databases. The job was an Oracle’s auto task running statistics gathering for more than 3 hours. I was curious to know why it took so long and…

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Do you have enough Redo?

The question of whether a database has enough redo logs available is quite common. The documentation suggests to use FAST_START_MTTR_TARGET and V$INSTANCE_RECOVERY.OPTIMAL_LOGFILE_SIZE to identify “the optimal” redo log size based on the target recovery time. I’ve never used it and…

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Batched table access

When I first saw the suffix BATCHED in an Oracle execution plan from 12c, I was curious to see what is hidden behind and how it works. I had some spare time for testing and wanted to share my findings…

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