Finding Cache Hit Ratios History

Many DBAs consider values of cache hit ratios as mythical, but I personally don’t think so as these have guided me to the right direction many times. But this is really true that by looking at cache hit ratios solely and making conclusions might really lead you to the wrong direction. These values can only be seen and analysed in some context.

ORA-15001: diskgroup does not exist or is not mounted

If you are having role separation for Grid Infrastructure (RAC or standalone) and Database software, you would need to have an OS user (normally named “grid”) for Grid Infrastructure installation and management, and an OS user (normally names “oracle”) for database software installation and management.

Universal Unique Identifier (UUID) error during 12c RAC Installation

During installation of 12.1.0.1 (12c) grid infrastructure (RAC or standalone), prerequisite check screen may show a warning for “Device Checks for ASM”, stating:
Cannot verify the shared state for device /dev/oracleasm/disk/<ASM Disk> due to Universally Unique Identifiers (UUIDs) not being found, o

Performing Block Media Recovery

While running SQL statements on the database, suddenly SQLs may start failing with error messages showing that there is database block corruption in some datafile(s). Error messages in the Alert Log could be similar to the following.

... ORA-01578: ORACLE data block corrupted (file # 4, block # 36321)

Installing Oracle 12c Release 1 RAC on Linux 6

This article explains how to install a 2 nodes Oracle 12c release 1 Real Application Cluster (RAC) on Oracle Linux 6. I did this installation on Oracle Virtual Box by creating 2 virtual machines with shared storage. OS platform I used is Oracle Enterprise Linux 6 (update 3), and Oracle GI and RDBMS version is 12.1.0.2. Same installation guide should work for Redhat Linux 6 also

Creating Virtual Machine using Oracle Virtual Box

DBAs can use Oracle Virtual Box to create virtual machines for testing purposes. Even Oracle RAC installation practice can be done using virtual machines by creating virtual shared storage for the virtual RAC nodes.

Following are the steps with screen shots for how to create a virtual machine using Oracle