Install guide

2. Create directories that correspond to the hostnames:

$ mkdir rac7

$ mkdir rac8

3. Create the admin directory in each directory:

$ mkdir rac7/admin

$ mkdir rac8/admin

4. Create the CPDN link (from each host).

ON RAC7, in $OH/network:

$ ln –s @ hostname admin

On RAC8, in $OH/network:

$ ln –s @ hostname admin

4.4. Oracle Settings and Suggestions

Among the thousands of tuning variables in Oracle, the 2 most important are SGA_T ARGET and

FILESYST EMIO_OPTIONS. Oracle performs more efficient I/O operations of the files on the GFS

volumes are opened with DirectIO (DIO) and AsyncIO (AIO). This is accomplished using the

filesystem io_options parameter:

filesystemio_options=setall

DirectIO bypasses the page cache for all I/O operations. If DIO is disabled, all datafile I/O will be use the

page cache, which effectively double buffers the I/O. Oracle already contains a page cache, called the db

block buffer cache. Double buffering increases response time latency for reads, and when the page

cache runs the server out of Free memory, system throughput usually drops by 30-50%.

The third most important init.ora parameter must be decided upon first: db_block_size. The

default db_block_size for Oracle on Linux is 8K. GFS uses 4K blocks (as does x64 hardware).

Although 4K blocks will out-perform 8K blocks in GFS, other factors in the application might mask this

effect. Application performance requirements take precedence, and do not change it unless you know

what you are doing. It is not recommended that 2K blocks be used on GFS. Most customers leave it 8K.

RAC/GFS was certified using both 4K and 8K blocks, but supports all block size values that the Oracle

RDBMS supports.

4.4.1. RHEL Settings and Suggestions

The RDBMS needs non-default values in the /etc/sysctl.conf that involve shared memory,

semaphores. Clusterware requires the network settings to be altered. These are documented in the

Oracle Install Guide or release notes for that particular version.

It is highly recommended that you install the 64-bit (x64) version of RHEL, Red Hat Cluster Suite and

Oracle. Although 32-bit (x86) platforms are still fully certified and supported by both Oracle and Red Hat,

Oracle performs better when allowed to access more memory.

4.4.2. Huge TLBs

Red Hat Enterprise Linux 5 Configuration Example - Oracle HA on Cluster Suite