All about headroom and mandatory patching before June 2019

This post was triggered upon rereading a blogpost by Mike Dietrich called databases need patched minimum april 2019. Mike’s blogpost makes it clear this is about databases that are connected using database links, and that:
– Newer databases do not need additional patching for this issue (11.2.0.4, 12.1.0.2, 12.2 and newer).
– Recent PSU patches contain a fix for certain older versions (11.1.0.7, 11.2. (more...)

Quick install of prometheus, node_exporter and grafana

This blogpost is a follow up of this blogpost, with the exception that the install method in this blogpost is way easier, it uses an Ansible playbook to do most of the installation.

1. Install git and ansible via EPEL:

# yum -y localinstall https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
# yum -y install ansible git

2. Clone my ‘prometheus_node_exp_grafana_install’ repository:

# git clone https://gitlab.com/FritsHoogland/prometheus_node_exp_grafana_install.git

3. Run the prometheus.yml playbook to install (more...)

Oracle database wait event ‘db file async I/O submit’ timing bug

This blogpost is a look into a bug in the wait interface that has been reported by me to Oracle a few times. I verified all versions from Oracle 11.2 version up to 18.2.0.0.180417 on Linux x86_64, in all these versions this bug is present. The bug is that the wait event ‘db file async I/O submit’ does not time anything when using ASM, only when using a filesystem, where (more...)

All about ansible vault

This blogpost is about using ansible vault. Vault is a way to encrypt sensitive information in ansible scripts by encrypting it. The motivation for this blogpost is the lack of a description that makes sense to me of what the possibilities are for using vault, and how to use the vault options in playbooks.

The basic way ansible vault works, is that when ansible-playbook reads a yaml file, it encounters $ANSIBLE_VAULT;1.1;AES256 indicating ansible vault (more...)

A re-introduction to the vagrant-builder suite for database installation

In a blogpost introducing the vagrant builder suite I explained what the suite could do, and the principal use, to automate the installation of the Oracle database software and the creation of a database on a virtual machine using vagrant together with ansible and virtual box.

This blogpost shows how to use that suite for automating the installation of the Oracle database software and the creation of a database on a linux server directly, with (more...)

A look into oracle redo, part 11: log writer worker processes

Starting from Oracle 12, in a default configured database, there are more log writer processes than the well known ‘LGWR’ process itself, which are the ‘LGnn’ processes:

$ ps -ef | grep test | grep lg
oracle   18048     1  0 12:50 ?        00:00:13 ora_lgwr_test
oracle   18052     1  0 12:50 ?        00:00:06 ora_lg00_test
oracle   18056     1  0 12:50 ?        00:00:00 ora_lg01_test

These are the log writer worker processes, for which the minimal amount is equal to the amount public (more...)

A look into oracle redo: index and overview

I gotten some requests to provide an overview of the redo series of blogposts I am currently running. Here it is:

https://fritshoogland.wordpress.com/2018/01/29/a-look-into-oracle-redo-part-1-redo-allocation-latches/
https://fritshoogland.wordpress.com/2018/02/05/a-look-into-oracle-redo-part-2-the-discovery-of-the-kcrfa-structure/
https://fritshoogland.wordpress.com/2018/02/12/a-look-into-oracle-redo-part-3-the-log-writer-work-cycle-overview/
https://fritshoogland.wordpress.com/2018/02/20/a-look-into-into-oracle-redo-part-4-the-log-writer-null-write/
https://fritshoogland.wordpress.com/2018/02/27/a-look-into-oracle-redo-part-5-the-log-writer-writing/
https://fritshoogland.wordpress.com/2018/03/05/a-look-into-oracle-redo-part-6-oracle-post-wait-commit-and-the-on-disk-scn/
https://fritshoogland.wordpress.com/2018/03/19/a-look-into-oracle-redo-part-7-adaptive-log-file-sync/
https://fritshoogland.wordpress.com/2018/03/26/a-look-into-oracle-redo-part-8-generate-redo/
https://fritshoogland.wordpress.com/2018/04/03/a-look-into-oracle-redo-part-9-commit/
https://fritshoogland.wordpress.com/2018/04/09/a-look-into-oracle-redo-part-9a-commit-concurrency-considerations/
https://fritshoogland.wordpress.com/2018/04/16/a-look-into-oracle-redo-part-10-commit_wait-and-commit_logging/

A look into oracle redo, part 10: commit_wait and commit_logging

The redo series would not be complete without writing about changing the behaviour of commit. There are two ways to change commit behaviour:

1. Changing waiting for the logwriter to get notified that the generated redo is persisted. The default is ‘wait’. This can be set to ‘nowait’.
2. Changing the way the logwriter handles generated redo. The default is ‘immediate’. This can be set to ‘batch’.

There are actually three ways these changes can (more...)

A look into oracle redo, part 9a: commit – concurrency considerations

During the investigations of my previous blogpost about what happens during a commit and when the data becomes available, I used breaks in gdb (GNU debugger) at various places of the execution of an insert and a commit to see what is visible for other sessions during the various stages of execution of the commit.

However, I did find something else, which is very logical, but is easily overlooked: at certain moments access to (more...)

A look into oracle redo, part 9: commit

The previous blogpost talked about a simple insert, this blogpost investigates what happens when the DML is committed. Of course this is done with regular commit settings, which means means they are not touched, which means commit_logging is set to immediate and commit_wait is set to wait as far as I know. The documentation says there is no default value, and the settings are empty in all parameter views. In my humble opinion, if you (more...)

A look into Oracle redo, part 5: the log writer writing

| Feb 27, 2018

This the the fifth blog in a series of blogposts about Oracle database redo. The previous blog looked into the ‘null write’ (kcrfw_do_null_write actually) function inside kcrfw_redo_write_driver, which does housekeeping like updating SCNs and posting processes if needed, this blog looks into what happens when the log writer is actually posted by a process or if public redo strand buffers have been written into. In part 3 of this blog series (the log writer working (more…)