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Franck Pachot

Franck Pachot

pgSentinel: the sampling approach for PostgreSQL

By | Database Administration & Monitoring, Postgres | 5 Comments

By Franck Pachot . Here is the first test I did with the beta of pgSentinel. This Active Session History sampling is a new approach to Postgres tuning. For people coming from Oracle, this is something that has made our life a lot easier to optimize database applications. Here is a quick example showing how it links together some information that are missing without this extension.

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Franck Pachot

Data Guard: always set db_create_file_dest on the standby

By | Oracle | 2 Comments

By Franck Pachot . The file name convert parameters are not dynamic and require a restart of the instance. An enhancement request was filled in 2011. I mentioned recently on Twitter that it can be annoying with Active Data Guard when a file on the primary server is created on a path that has no file name conversion. However, Ian Baugaard mentioned that there is a workaround for this specific case because db_create_file_dest is dynamic:

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Franck Pachot

My tmux scripts to script demos

By | Oracle | No Comments

By Franck Pachot . When I did my first demo using tmux, I have written the following blog post to explain it: https://blog.dbi-services.com/using-tmux-for-semi-interactive-demos/. Since then I’ve done all my demos with this technique. My scripts and configuration files have evolved now I have uploaded the on GitHub to share them: https://github.com/FranckPachot/scripts/tree/master/tmux-demo

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Franck Pachot

18c: Order by in WITH clause is not preserved

By | Oracle | One Comment

By Franck Pachot . For a previous post I’ve run on 18c a script of mine to get the V$MYSTAT delta values between two queries. This script (new version available on GitHub) generates the queries to store some values and subtract them on the next execution. But I had to fix it for 18c because I relied on some order by in a CTE which is lost in 18c. The idea was to get the…

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Franck Pachot

18c: some optimization about redo size

By | Oracle | One Comment

By Franck Pachot . Some years ago, at the time of 12.1 release, I published in the SOUG newsletter some tests to show the amount of redo generated by different operations on a 10000 rows table. I had run it on 12.2 without seeing the differences and now on 18.1 I get the statistics from mystat using a script that displays them as columns, with the value being the difference from the previous run. I’ve…

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Franck Pachot

Event Sourcing: CQN is not a replacement for CDC

By | Oracle | 3 Comments

By Franck Pachot . We are in an era where software architects want to stream the transactions out of the database and distribute them, as events, to multiple microservices. Don’t ask why, but that’s the trend: store inconsistent eventually consistent copies of data in different physical components, rather than simply using logical views in the same database, where the data is ACIDely stored, processed and protected. Because it was decided that this segregation, in CQRS…

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Franck Pachot

Statspack installation scripts

By | Oracle | 11 Comments

By Franck Pachot . When Diagnostic Pack is disabled, either because you don’t have Diagnostic Pack or you are in Standard Edition, I highly recommend to install Statspack. When you will need it, to investigate on an issue that occured in the past, you will be happy to have it already installed and gathering snapshots.

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Franck Pachot

PGIO, PG_STAT_ACTIVITY and PG_STAT_STATEMENTS

By | Oracle, Postgres | No Comments

By Franck Pachot . For an Oracle DBA, we are used to join active sessions (from V$SESSION where status=’ACTIVE) with active statements (from V$SQL where users_executing>0) on the SQL_ID. V$ACTIVE_SESSION_HISTORY also displays the TOP_LEVEL_SQL_ID to get the entrypoint of the usercall if we need it. With Postgres it is a bit more difficult because it seems that PG_STAT_ACTIVITY do not show the active statement but only the top-level one. But pg_stat_statement collects statistics for the…

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Franck Pachot

Lighty for PostgreSQL

By | Database Administration & Monitoring, Postgres | No Comments

By Franck Pachot . If you follow this blog, you should know how I like Orachrome Lighty for Oracle, for its efficiency to monitor database performance statistics. Today Orachrome released the beta version of Lighty for Postgres: https://orachrome.com/news/la-beta-de-lighty-for-postgresql-est-ouverte/ The Cloud is perfect to do short tests with more resources than my laptop, especially the predictability of performance, then I started a Bitnami Postgres Compute service on the Oracle Cloud and did some tests with pgbench…

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Franck Pachot

Kernel panic – not syncing: Out of memory and no killable processes

By | Operation systems, Oracle | One Comment

By Franck Pachot . This is a quick post to give a solution (maybe not the best one as this was just quick troubleshooting) if, at boot, you see something like: Trying to allocate 1041 pages for VMLINUZ [Linux=EFI, setup=0x111f, size=0x41108d01] and then: Kernel panic – not syncing: Out of memory and no killable processes Pid: 1228 comm: kworker Not tainted 3.8.13-118.17.4.el6uek.x86_64 #2

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