Location of ASM tablespace files

Login as "grid"

export ORACLE_HOME=/u01/app/12.1.0/grid --this is also usual installation directory

export ORACLE_SID=+ASM

cd $ORACLE_HOME/bin

./asmcmd -p

ASMCMD>ls
+DATA01
+DATA02
ASMCMD>cd +DATA01

How to Fix Yum Error: database disk image is malformed

Possible Cause For Error

Yum is a well known tool used for installing packages on RPM based Linux distributions. It is most widely used package manager on Redhat Enterprise Linux, CentOS and Fedora operating systems.
Any other operating system derived from these distributions also use Yum for the installation, update or removal of software packages.
If you are encountering following error message while updating or installing any packages, its obvious that something bad has happened to Yum.

Error: database disk image is malformed

It usually occurs once “yum update” process is interrupted, quite possible that your system went powered off during  “yum update” process and it left yum database in a corrupt state, all we need to do is to clean and repair yum database to fix the error.

Fixing this Yum’s error

There are few steps to resolve this error, all pretty simple.

Clear Yum Caches

Clear yum cache by running the following command. It will ensure to remove entries from /var/cache/yum/ directory
Please note that it will not effect any of your currently installed packages. Pretty safe command to run

yum clean all

Clear Yum’s XML meta data by running the following command:

yum clean metadata 

Run following command to clear the cached files for database.

yum clean dbcache

It is important to clear Yum’s make cache, use following command:

 yum makecache 

Rebuild RPM Database

As the last step, make sure to rebuild your system’s RPM database. Run following two commands to achieve this.

mv /var/lib/rpm/__db* /tmp 

rpm –rebuilddb 

OIM/OAM 12c RCU Creation failed for Oracle Database 12c

Issue:

When we run RCU utility to create OIM/OAM Schemas, the following error is encountered
Mon Jul 24 13:36:02.696 UTC 2018 ERROR assistants.rcu.backend.task.PrereqTask: oracle.sysman.assistants.rcu.backend.task.PrereqTask::execute: Prereq Evaluation Failed
oracle.sysman.assistants.rcu.backend.validation.PrereqException:
ERROR – RCU-6083 Prerequisite check failed for selected component:
CAUSE – RCU-6083 Prerequisite check failed for selected component.
ACTION – RCU-6083 Refer to the RCU logs for additional details. Make sure that the prerequisite requirements are met.
Refer to RCU log at /tmp/RCU2018-07-24_13-30_1931354565/logs/rcu.log for details.
at oracle.sysman.assistants.rcu.backend.validation.PrereqEvaluator.executePrereqTask(PrereqEvaluator.java:713)
at oracle.sysman.assistants.rcu.backend.task.PrereqTask.execute(PrereqTask.java:68)
at oracle.sysman.assistants.rcu.backend.task.ActualTask.run(TaskRunner.java:346)
at java.lang.Thread.run(Thread.java:748)
Mon Jul 24 13:36:02.697 UTC 2018 ERROR assistants.rcu.backend.task.ActualTask: oracle.sysman.assistants.rcu.backend.task.ActualTask::run: RCU Operation Failed
oracle.sysman.assistants.common.task.TaskExecutionException:
ERROR – RCU-6083 Prerequisite check failed for selected component:
CAUSE – RCU-6083 Prerequisite check failed for selected component.
ACTION – RCU-6083 Refer to the RCU logs for additional details. Make sure that the prerequisite requirements are met.
Refer to RCU log at /tmp/RCU2018-09-24_13-30_1931354565/logs/rcu.log for details.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Error: Views/Synonyms required for XA transaction support are missing in this Database 12c.
These views/synonyms are required by the OIM Schema.
Action: Refer Oracle Database Administrator’s Guide to install XA transaction recovery views/synonyms using the script xaview.sql. Contact your DBA.
For Database12c CDB config: execute xaview.sql from PDB SYS user
For Database12c NON-CDB config: execute xaview.sql from CDB SYS user

Resolution:

Step 1
Login to your database as sys or any other user with sysdba privileges and run below two scripts

@$ORACLE_HOME/javavm/install/initxa.sql
@$ORACLE_HOME/rdbms/admin/xaview.sql

Step 2
Along with the above views, make sure following parameters are tuned as per Oracle's recommendation
PROCESSES (min > 300)
NLS_LENGTH_SEMANTICS (BYTE)
SHARED_POOL_SIZE ( min > 200MB)
SGA_MAX_SIZE (min > 200MB)
DB_BLOCK_SIZE (min > 8k)
OPEN_CURSORS (min > 1000)