The Problem On CentOS/RHEL 6, a disk has issue and mdadm command shows /dev/md5 was active, degraded state . # mdadm -Q --detail /dev/md5 /dev/md5: Version : 0.90 Creation Time : Wed Apr 12 09:50:21 2017 Raid Level : raid1 Array Size : 10485696 (10.00 GiB 10.74 GB) Used Dev Size : 10485696 (10.00 GiB 10.74 GB) Raid Devices : 2 Total Devices : 1 Preferred Minor : 5 Persistence : Superblock is persistent Update Time : Mon Jun 5 14:47:09 2017 State : active, degraded Active Devices … [Read more...] about mdadm Command Shows State : active, degraded
Archives for December 2018
How to Re-generate initramfs and vmlinuz for Rescue Kernel with Current Kernel in CentOS/RHEL 7
We want to re-generate initramfs and vmlinuz for the Rescue Kernel in our CentOS/RHEL 7 system. How can this be done using the current kernel from which the system is booted up? During the boot process, when the kernel image and initramfs image get loaded, initramfs starts the first process on the system, which is systemd with the process ID 1. This systemd process further takes over control in the final stages of system booting and performs the following operations: Reads the … [Read more...] about How to Re-generate initramfs and vmlinuz for Rescue Kernel with Current Kernel in CentOS/RHEL 7
Simple Steps to use LogMiner for finding high redo log generation
LogMiner is a tool that lets you use SQL statements to analyze events in the database log. With LogMiner, you can track transactions as they are processed or locate specific functions that result in data modifications. LogMiner was introduced with Oracle8i. LogMiner can be used, along with audit trails, to determine what has happened in your Oracle database. In this post, we will see simple steps for mining the redo logs, for instance, to troubleshoot excessive redo generation. 1. Enable … [Read more...] about Simple Steps to use LogMiner for finding high redo log generation
Beginners Guide to “journalctl” – How To Use Journalctl to View and Manipulate Systemd Logs
Using the system journal By default, newer systemd based linux systems now uses two logging services for the system logs: systemd-journald, which is configured to only keep logs in memory rsyslogd, which gets messages sent to it by systemd-journald (and others) and stores them on disk. To view messages in the system journal, a tool called journalctl can be used. If used without any parameters it will show the full contents of the system journal, presented in a pager (by default less is … [Read more...] about Beginners Guide to “journalctl” – How To Use Journalctl to View and Manipulate Systemd Logs
How to find the size of a MySQL database
The easiest method is to query the INFORMATION_SCHEMA. For Example: SELECT ENGINE, COUNT(*), SUM(DATA_LENGTH), SUM(INDEX_LENGTH) FROM information_schema.TABLES WHERE TABLE_SCHEMA='menagerie' GROUP BY ENGINE; Additionally here is a potentially faster example to estimate the db size (InnoDB only and if you do not use compressed tables) since it doesn't use INFORMATION_SCHEMA.TABLES : select sum( CLUST_INDEX_SIZE + OTHER_INDEX_SIZE)* @@innodb_page_size / 1024 / 1024 "Estimated size in Mb" … [Read more...] about How to find the size of a MySQL database
How To Automate The Opening Of Pluggable Databases After The CDB Starts Up in Oracle 12c
Here is a short note on how to automate the startup of PDBs after the CDB starts up in Oracle database 12c. You can start all the PDBs or selective PDBs using below steps. We will need to create a database startup trigger in order to automate the PDB startup. Follow the steps outlined below. 1. Login into the CDB as sysdba. $ sqlplus / as sysdba 2. Create a database startup trigger to open all pluggable databases. create or replace trigger open_all_pdbs after startup on … [Read more...] about How To Automate The Opening Of Pluggable Databases After The CDB Starts Up in Oracle 12c