Database Administration & Monitoring

Flashback logging overhead: ‘db file sequential read’ on UNDO tablespace

By Franck Pachot . in my previous post I’ve reproduced an issue where some bulk insert into a GTT was generating too much undo. But the real case I encountered was worse: the insert was reading lot of(…)

Oracle: an unexpected lock behavior with rollback

By Franck Pachot . Here is an odd Oracle behavior I observed when a transaction that acquired a lock is rolled back. Note that this is related to a specific combination of locks that should not be encountered in(…)

Oracle 12.1.0.2: Wait event histograms in μs

By Franck Pachot . When an Oracle Database spends a high percentage of its DB time in User I/O, I usually check the wait event histograms in order to see if the storage system is working well. But today,(…)

Linux: how to monitor the nproc limit

By Franck Pachot . You probably know about ‘nproc’ limits in Linux which are set in /etc/limits.conf and checked with ‘ulimit -u’. But do you know how to handle the monitoring and be alerted when you’re close the fixed(…)

Oracle Exadata – poor optimization for FIRST_ROWS

By Franck Pachot . In a previous blog, I discussed the difference between rownum and row_number(), in particular their behaviour in implicitely adding a first_rows(n) to the optimizer. That reminded me that I forgot to blog about an(…)

Best practice for the sending of an Oracle execution plan

By Franck Pachot . You have a query that takes too long and you want help to analyze the execution plan? Then you need to get it with relevant information, and correctly formatted. Autotrace is not a good option(…)

Archivelog deletion policy for Standby Database in Oracle Data Guard

By Franck Pachot . Do you use ARCHIVELOG DELETION POLICY TO APPLIED ON ALL STANDBY for your Oracle databases in Data Guard? Maybe you also use the Fast Recovery Area as archive log destination. That’s good practice! But did(…)

SQL Server 2012: First Hotfix for Service Pack 1 available

This month, Microsoft has released the first hotfix for SQL Server Service Pack 1. Analysis This Hotfix concerns the installation of SQL Server components and Analysis Services. If you have installed the RTM version with Analysis Service and successfully installed(…)

SQL Server 2012: Feature Pack

Since the third CTP version of SQL Server 2012 codename Denali, you have some features available to provide an additional value for Microsoft® SQL Server 2012 like the other SQL Server versions. This Feature Pack or Manageability Tool Kit are(…)

Diving into Databases

By dbi services, we are a few poeples passionate by diving.We take this opportunity to let you dive into the two databases lakes Oracle and SQL server and see their similarities and differences. For this first level of diving(…)