Monday, April 3, 2017

How to install X Windows on Linux

The following packages (a.k.a RPMs) are required to setup X Windows on Linux, specifically Oracle Enterprise Linux (OEL) with the UEK kernel. It is tested successfully on Oracle Linux 7 update 3 for x86_64. These packages also install KDE as the default desktop environment on this Linux operating system.

Login as root and run the yum install package command for each such package below.

yum install vnc
yum install vnc-server 
yum install xterm
yum groupinstall "X Window System"  
yum install kdebase
yum install gnome-terminal
yum groupinstall "KDE"

Monday, January 2, 2017

TNS-01189: The listener could not authenticate the user

In older versions of Oracle database such as Oracle 9i etc, one can stop a listener remotely. This was a serious security problem because all that is needed by any client or end user is the listener name and a TNS entry(listener port and host name) to shutdown the listener sitting from that client machine !!!. This can be prevented by securing the listener with a password. We published a blog post about this security issue a few years ago.

But this password feature is deprecated since Oracle database 11g R2 release. This is no security problem because the listener is now secured using local operating system authentication. Therefore, no client or end user can remotely shutdown a database listener anymore.  If one attempts to stop a database listener process from a remote machine, one receives the error "TNS-01189: The listener could not authenticate the user".  A listener can be only be stopped after logging into the database server (and connecting to the Oracle software owner account) that hosts the listener process. This experience is similar to how Oracle does not allow remote connections to the sys built-in administrative database account.

Therefore, there is no need of protecting Oracle database listeners with passwords since Oracle database 11g R2 release.

Saturday, June 11, 2016

Microsoft SQL Server 2016 DBA Training

DBA University is excited to announce MS SQL Server 2016 DBA Training online course. Each training schedule runs for a period of 40 hours spread over 7 weeks. The training sessions are held from 7:30 pm to 9:30 central time Monday, Tuesday and Sunday each week.

Course Highlights

1) 40 hours course duration.
2) Training will be on the latest Microsoft SQL Server 2016 version.
3) Monday, Tuesday, Sunday - 7:30 pm Central Time to 9:30 pm Central Time online.
4) Training materials available for download through Dropbox link.
5) Click here for a FREE DEMO session  (Name and Email only)

Lab work

1) Each student will get a remote lab computer to practice the course work.  
2) The training will be on Microsoft SQL Server 2016 version with Windows Server 2012 R2 as the operating system.
3) 10 hours Remote LAB access on Saturday, Sunday
4) 6 hours Remote LAB access on weekday evenings.
5) Students can use the Windows Remote Desktop Connection program to connect to the remote lab server.

Links and Resources

2) Click here for a FREE DEMO session  (Name and Email only)
3) Click here to register for the online training course

Friday, May 20, 2016

How to restart Oracle dbca after a failed database creation with ASM


This article provides you the details how to clean up the files created by dbca tool as part of a partially created Oracle database using Oracle Automatic Storage Management (Oracle ASM). Let us assume the ASM instance name is +ASM, the ASM diskgroup name is +DATA, the Oracle database name that failed to be created successfully as SALESDB with 12c R1 version.

This article also provides the steps to remove all references that still exist for the SALESDB database before a retry.


1) .  oraenv  (Note the space after the DOT symbol. Set +ASM environment)
2) echo  $ORACLE_SID  (Must show +ASM)
3) sqlplus /  as  sysasm
4) select  name from  v$asm_alias;

Let us find the control file alias name of the failed SALESDB database. It starts with Current. For example, it may be Current.257.912291913. Therefore the full path of the control file in ASM diskgroup is +DATA/SALESDB/CONTROLFILE/Current.257.912291913

5) exit
6) . oraenv (Note the space after the DOT symbol. Set SALESDB environment.)
7) echo  $ORACLE_SID  (Must show SALESDB.)
8) cd  $ORACLE_HOME/dbs

9) Remove any existing initSALESDB.ora or spfileSALESDB.ora that was created during the initial execution of dbca.
10) vi initSALESDB.ora  (Add the below initialization parameters.)


11) sqlplus / as sysdba
12) startup mount force restrict;
13) exit
14) rman
15) connect /
16) drop database;
17) exit
18) Delete the initSALESDB.ora
19) Remove the SALESDB entry in /etc/oratab file.
20) cd $ORACLE_BASE/fast_recovery_area
21) rm -rf SALESDB (Delete any files created by dbca in the Fast Recovery Area.)
22) cd $ORACLE_BASE/admin
23) rm -rf SALESDB
24) cd $ORACLE_BASE/diag/rdbms
25) rm -rf salesdb (Delete the diagnostic files directory structure for SALESDB.)
26) cd $ORACLE_BASE/cfgtoollogs/dbca
27) rm -rf SALESDB


Once the above steps are completed, the +DATA diskgroup should not have any more ASM files for the SALESDB database. Also, all SALESDB references on the database server will be removed. Finally, start the dbca tool again and this time, hopefully, your SALESDB database creation will be successful.

Wednesday, May 4, 2016

oracle training on demand

We are pleased to announce that DBA University is now offering all Oracle training courses on demand.


1) Each student gets 3 months of on demand access to a recently concluded live training course through our high quality cloud based videos. 
2) Students also get all the training materials through Dropbox downloads.
3) Two months of dedicated access to our cloud based remote lab servers.

Registration  Please click here for registration.

Oracle on demand training courses

Related Posts Plugin for WordPress, Blogger...