Friday, May 11, 2018

Initial Configuration of Fusion Middleware after the Installation

After completing Fusion Middleware installation installation, next step is initial configuration of the it. If you have done Fusion Middleware Installation, you would need to configure certain schemas (this is not needed for Weblogic and Coherence installation using generic installer) before you can create domains and start using Fusion Middleware. Click here for the official documentation.
Following are the schemas that need to be created

Monday, May 7, 2018

ORA-02095: specified initialization parameter cannot be modified


This is a generic error message that may be returned while setting an initialization parameter. There are a few other error messages that we may face and in this article, I would discuss those error messages as well. The most common reason of this error message is modifying a parameter using ALTER SYSTEM command that is not dynamically modifiable. In this case, we need to set the parameter in spfile, or pfile, and then a re-bounce of the instance would set the value of this parameter in the instance.

Tuesday, May 1, 2018

Installing Oracle Fusion Middleware 12.2 on Linux 6, Linux 7 and Windows

Oracle Fusion Middleware contains many products, tools, and services, and provides facility of using Java EE and developer tools, integration services, identity services, business intelligence and several other Oracle products.
In this article I would demonstrate how to install Oracle Fusion Middleware 12.2 (I am using 12.2.1.2.0 for this article) on Linux 6 and Linux 7. Following is the official document that I used while writing this article.

Monday, April 23, 2018

ORA-01013: user requested cancel of current operation


If ORA-01013 appears in the alert log file, it would mean that your application is closing a session forcefully and database records this as action canceled by the user/application (as name description of this error suggests). It would mean that most of the time it is not something that can be handled from the database side to stop this message from appearing in the alert log file. But, sometimes this error may be because Oracle internally kills some process that crosses a timeline already defined. In the following I would provide further detail of this.

Tuesday, April 17, 2018

Error 12154 received logging on to the standby

There are several error messages related to dataguard environment and many of them have been discussed in my blog, and you can find links to those articles at the bottom of this article. In this article, I will explain Error 12154 that I received in one of my dataguard environments. This error message may appear in the alert log file of your primary database and it would seem similar to the following.
Error 12154 received logging on to the standby
FAL[client, USER]: Error 12154 connecting to <FAL_SERVER> for fetching gap sequence

Friday, April 13, 2018

Error 1033 received logging on to the standby



Troubleshooting a dataguard environment is not very straightforward sometimes. If you come to know that physical standby database is out of sync with the primary database, first thing is to check the alert log files of primary and standby database to find out any error messages that might be appearing in the alert log files. For example, if error 1003 is reported in the alert log file, you may see entries similar to the following in the primary database’s alert log file.
Mon Feb 06 00:10:40 2017
Error 1033 received logging on to the standby
PING[ARC1]: Heartbeat failed to connect to standby 'MY_STANDBY_DB'. Error is 1033.

Monday, April 2, 2018

Starting and Stopping Grid Infrastructure on a Standalone GI Installation



This document explains how to start and stop an Oracle cluster. To start and stop Grid Infrastructure services for a standalone installation, there are slightly different commands. Using same commands as RAC to start and stop the GI resources would return errors as follows
[root@~]$ /u01/app/11203/grid/bin/crsctl stop crs
CRS-4013: This command is not supported in a single-node configuration.
CRS-4000: Command Stop failed, or completed with errors.
[root@ ~]$ /u01/app/11203/grid/bin/crsctl stop cluster -all
CRS-4013: This command is not supported in a single-node configuration.
CRS-4000: Command Stop failed, or completed with errors.

Monday, March 26, 2018

Finding IO statistics in Linux Environment for Slow Disks


I have written 2 articles (AWR 1, AWR 2) in relation to the disk latency and how to read AWR reports to investigate IO slowness. In this article I will explain how we check disks IO performance in Linux systems. We will check how the disks where our datafiles and redo log files are stored are performing. These disks could be simple Linux mount points, or ASM disks. In case of ASM, we will need to find out the disks that are part of ASM diskgroups so that we can check the performance of those disks. For example, following is the way how we can find out the disks that are part of ASM diskgroup.

Monday, March 19, 2018

Reading and Understanding AWR Report for IO or Disk latency - 2



This a second article regarding IO latency issues investigation using AWR. First article can be found here. In this article I will further explain about checking IO latencies at the OS level in Linux

Log file sync

We had a production server running on Virtual Machine (vmware), and after a downtime, we started receiving complains about slow database. AWR report showed that “log fie sync” wait event that comes under COMMIT wait class was at the top, and database was spending more than 30% of its time on log file sync wait. Log file sync wait even can be observed in a very busy OLTP database, but it should not consume this much time as we were seeing, and should be found at the bottom of the list of top wait events.

Monday, March 12, 2018

Reading and Understanding AWR Report for IO or Disk latency - 1

Recently I performed a failover of my Oracle database (running on Linux) to my standby database, and after the switchover, application team started complaining about extreme slowness. I was using OEM Cloud Control and the graph was showing high waits for “free buffer wait” and alert log started showing Checkpoint not Complete.  Since I never saw these waits on my previous primary server (now standby), so first thing came into my mind was that the disks on the standby server (now primary) are probably very slow, because hardware of my servers was very old. Servers also had internal disks (not SAN or NAS). I generated AWR report for the time when database was running fine and without any performance issue, and then a latest time report based on latest snapshots to see what is going wrong with the IO.

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