Sunday, November 19, 2017

CRS-4700: The Cluster Time Synchronization Service is in Observer mode

This is very important to keep the time of cluster nodes synchronized across the cluster. Time difference among nodes can cause issues, and sometime it can cause the node(s) restart.

There are 2 ways of keeping the time synchronized across the RAC nodes: using NTP at OS level, or using Cluster Time Synchronization Service that runs as a RAC resource.

Sunday, November 12, 2017

Segment Space Growth History and Forecast

I have already written articles to get tablespace space usage history and forecast (10g and 11g, 12c and above) and database space usage history and forecast (10g and 11g, 12c and above). Here, I will explain how we can get the same information about segments, and can forecast the future growth of segments.

Sunday, November 5, 2017

ORA-39510 While Starting Cluster Health Monitor Repository (MGMTDB)

MGMTDB, also called Management Repository Database was introduced in 12c Grid Infrastructure. This repository database is used to store Cluster Health Monitor data so that this monitoring data can be used for Grid Infrastructure troubleshooting. This database resource is set to start automatically on the start of Grid Infrastructure, but, there could be some scenarios where MGMTDB might not start because of some issues. One of the similar problems I face because of which MGMTDB could not start automatically. When I tried to start Management Repository Database manually, it failed to start and threw following error messages.

Sunday, October 29, 2017

ORA-00313 ORA-00312 ORA-17503 ORA-15173 in Standby Alert Log File

Errors in file /u01/app/oracle/diag/rdbms/standby_db/standby_db/trace/standby_db_lgwr_393229.trc:
ORA-00313: open failed for members of log group 12 of thread 2
ORA-00312: online log 12 thread 2: '+FRA_DG/standby_db/redolog12_02.rdo'
ORA-17503: ksfdopn:2 Failed to open file +FRA_DG/standby_db /redolog12_02.rdo

Monday, October 23, 2017

Creating a Real Application Cluster(RAC) 12c database using DBCA

After installing Oracle RAC, next step is to create a RAC database. Following is the process of creating a RAC database using dbca. Same method works on Windows or Unix based platforms.To invoke dbca, open a command line and run command “dbca”. On Windows, DBCA can also be invoked from Program Menu..

Tuesday, October 10, 2017

Oracle Flex Cluster

Oracle Real Application Cluster is a feature that was first introduced in Oracle 9i (Oracle Parallel Servers was a similar feature available before 9i, but not as robust as RAC) and has been an essential part of Oracle’s Maximum Availability Architecture. Since its advent in Oracle 9i, it has evolved a lot. Oracle 9i onward, every new release of Oracle has introduced something new in RAC which made it even more resilient, fault tolerant, and easy to manage architecture.
    

Tuesday, September 5, 2017

Oracle Flex ASM

Starting 12c, Oracle has introduced two very interesting features to add up to MAA (Maximum Availability Architecture), Oracle Flex Cluster and Oracle Flex ASM. In this article I will be explaining and demonstrating about Oracle flex ASM.
In flex ASM, you don’t need ASM instance to be running on each node (the Hub Node) because database instance can communicate with some other ASM instance running on any other node in the cluster.

Tuesday, July 25, 2017

Oracle Patches Types

In Oracle, there are different types of patching available; there are several types of patches released by Oracle that could be applied to the software you are running. There are on-off patches to fix bugs, regularly released patches, and security patches. In the following I will explain about different types of patches that are available to be installed on your RDBMS software.

Saturday, July 15, 2017

Installing Oracle 12c Release 2 RAC on Linux 6 and Linux 7

This article explains how to install a 2 nodes Oracle 12c Release 2 Real Application Cluster (RAC) on Oracle Linux 6 and 7. I did this installation on Oracle Virtual Box by creating 2 virtual machines with shared storage. OS platform I used is Oracle Enterprise Linux 7, and Oracle GI and RDBMS version is 12.2. Same installation guide should work for Linux 6 also as there are only a couple of differences in the steps that I will explain during this installation. There will be no difference in installation steps if there are more than 2 nodes in the RAC setup.

Friday, July 7, 2017

Running cluvfy (Cluster Verification Utility) during 12c R2 RAC installation


Following is the output of cluster verification utility that I executed during 12c R2 RAC installation. You can see 2 examples in the following. Example 1 demonstrated if you don’t have passwordless SSH connectivity configured for “grid” and “oracle” users, so you will need to execute this from each node one by one. Following output is from one node only.

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