Starting with Oracle 11g Oracle added several compression algorithms to compress data. They can be used for compressing tables, LOBs , compressed data pump exports or even RMAN backups. Unfortunately for some compression algorithms you need to purchase the “Advanced Compression Option”. The following table lists the available RMAN compression options, the most likely compression algorithm being used and states if an additional license is required:

RMAN Compression Type	Compression Algorithm used	Adv. Compression License required?	Backup set size	CPU Load
BASIC	BZIP2 (100k record size?)	No	small	medium to high
NONE	none	No	largest; approx. db size	extremely small
LOW	LZO	YES	somewhat smaller than using NONE	low
MEDIUM	ZLIB	YES	medium	medium
HIGH	BZIP2 (900k record size?)	YES	smallest	highest

This article is intended to take a look at the different compression methods available in Oracle 11g and to compare them.

Read more…

The following is a short guide on how to calculate the required kernel parameters for running Oracle 11g Release 2 database on Linux.

In addition to that i add some parameters recommended by myself.

Note that for running Oracle Grid Infrastrucure (aka “Clusterware”) some additional parameters might be required.

Read more…

In this and the following posts i will perform some crash and recover scenarios and show how to recover the cluster successfully.

At the moment the following tests are planned and will be published during the next days:

• suddenly turning off the power and restarting the node
• terminating private network connect between the cluster nodes
• recovering an ACFS file system which will not mount automatically
  (was not able to reproduce more than once; sorry guys)
• overwriting the ASM disk header with the disk group being offline
• corrupting an online and active ASM disk by writing chunks of random data to the disk randomly
• simulating disk errors by removing the device from the operating system
• corrupting  the OCR
• corrupting the Voting Disk

The environment used for the posts are explained in detail here.

Useful scripts can be found here.

Test #4: Corrupting the ASM disk with ASM disk group being online and active

After overwriting the ASM disk header while the disk group was offline we will now put some load on the full running cluster and corrupt the asm disk slightly.

Read more…

The following post is a summary of my tests with DBFS on a 11g Release 2 RAC.

DBFS – An Overview

Since the introduction of LOBs the database was used to store all kinds of files, for instance images, audio files, video files or even text files. Starting with Oracle 11g Release 1 introduced SecureFiles which introduced compression and de-duplication.

Oracle Database Filesystem (DBFS) creates a mountable file system which can be used to access files stored in the database as SecureFile LOBs. DBFS is a shared file system like NFS and consists of a server (the database) and a client. Just like a traditional database connection server and client can be on different systems which communicate over SQLNet. The same applies to DBFS as well.

The following figure illustrates DBFS:

(Source: http://download.oracle.com/docs/cd/E11882_01/appdev.112/e10645/adlob_fs.htm)

Read more…

There is a problem with shared oracle homes on ACFS documented here.

However if you have not configured SSH equivalence before this short guide shows how to do set up ssh equivalence between the nodes “rac1.regner.de” and “rac2.regner.de”:

1. Unpack the database installation files

2. Execute:

<PATH_TO_DATABASE_INSTALLATION>/sshsetup/sshUserSetup.sh
  -user ora11p -hosts "rac1.regner.de rac2.regner.de" -shared

Arguments:
-user: the name of the user for ssh equivalence to be configured
-hosts: space separated list of node names
-shared: indicates a shared oracle home (on acfs or nfs)

3. Check it

/usr/bin/ssh -o FallBackToRsh=no  -o PasswordAuthentication=no 
  -o StrictHostKeyChecking=yes  -o NumberOfPasswordPrompts=0 rac2 /bin/date

/usr/bin/ssh -o FallBackToRsh=no  -o PasswordAuthentication=no
  -o StrictHostKeyChecking=yes  -o NumberOfPasswordPrompts=0 rac1 /bin/date

The two commands above should return the current date. Thats it.

This is the final part of the Oracle 11g Release 2 installation guide. At this point you should have:

• Oracle database and grid infrastructure binaries installed
• at least ONE or better two disk groups configured for:
  • database and binary files
  • flash recovery area

Our database name will be “ORA11P”.

Preparations

• create directory for cfgtools

create /u01/app/oracle/cfgtoollogs
mkdir -p /u01/app/oracle/cfgtoollogs
chown root:dba /u01/app/oracle/cfgtoollogs
chmod 775 /u01/app/oracle/cfgtoollogs

• Check SSH equivalence once again:
  execute as user „ora11p“ (this is the user holding the oracle database binary installation):

/usr/bin/ssh -o FallBackToRsh=no  -o PasswordAuthentication=no 
  -o StrictHostKeyChecking=yes  -o NumberOfPasswordPrompts=0 rac2 /bin/date

/usr/bin/ssh -o FallBackToRsh=no  -o PasswordAuthentication=no 
  -o StrictHostKeyChecking=yes  -o NumberOfPasswordPrompts=0 rac1 /bin/date

Both commands should return the current date. If there are errors like „connection refused“, check:

• network connectivity between both nodes
• does a „normal“ SSH connection works?:
  • ssh root@rac1-priv
  • ssh root@rac1
  • ssh root@rac2-priv
  • ssh root@rac2

both commands should prompt for a password.

If SSH was working before and seems “gone” you might face a problem documented here.

• add ACFS oracle home to cluster registry

$GRID_HOME/bin/srvctl add filesystem -d /dev/asm/ora11p_home-132
  -v ora11p_home -g DATA2 -m /u01/app/oracle/product/11.2.0/ora11p -u ora11p

Arguments:
-d: path of advm volume
-v: name of volume
-m: mount point path

„-u ora11p“ ist important and must match the owner of the database binary installation; else dbca will raise error compaining about missing permissions

Create the database with dbca

Start dbca

Where to go now?

• Tune Instance, for instance:
  • memory_target
  • db_writer_processes
  • sessions parameter
  • …
• Configure, perform and test your backup

Starting with Oracle 11g Release 2 Oracle introduced a new cluster database connection concept: SCAN – “Single Client Access Name”.

SCAN on the server side

When installing a 11g Release 2 grid infrastructure you are asked for the cluster name which will be part of the SCAN. The notation for the SCAN is:

<clustername>-scan.<domain>

For instance if your cluster is named “rac” and the domain “regner.de” the SCAN name will be “rac-scan.regner.de”.

In order to successful install grid infrastructure you need to configure your DNS (hosts file entries will not work!) prior installing grid infrastructure to resolve the name accordingly. Oracle requires at least one, better three IPs configured for the scan name. Your DNS zone file might look like this:

 

In the example zone file above we configured three IPs for the scan: 172.23.15.3, 172.23.15.4 and 172.23.15.5.

After installation you will find three listener processes running (separated on all cluster nodes) as shown in the following figure:

Listener for SCAN2 and SCAN3 are running on node “rac1″ and listener for SCAN1 is running on node “rac2″. For each SCAN listener there will be a dedicated network interface running with the same IP as configured in DNS:

Client connections

Connection to database “RAC11P” using SCAN would use this tnsnames entry:

RAC11P =
 (DESCRIPTION=
 (ADDRESS=(PROTOCOL=tcp)(HOST=rac-scan.regner.de)(PORT=1521))
 (CONNECT_DATA=(SERVICE_NAME=RAC11P))
 )

The ”old fashioned” way still works:

RAC11P_old =
 (DESCRIPTION=
 (ADDRESS_LIST=
 (ADDRESS=(PROTOCOL=tcp)(HOST=rac1-vip.regner.de)(PORT=1521))
 (ADDRESS=(PROTOCOL=tcp)(HOST=rac2-vip.regner.de)(PORT=1521))
 )
 (CONNECT_DATA=(SERVICE_NAME=RAC11P))
 )

Connecting to a named instance:

RAC11P =
 (DESCRIPTION=
 (ADDRESS=(PROTOCOL=tcp)(HOST=rac-scan.regner.de)(PORT=1521))
 (CONNECT_DATA=(SERVICE_NAME=RAC11P)
 (INSTANCE_NAME=RAC11P1))
 )

Today i came across a strange phenomenon:

I set up ssh equivalence during database installation but after rebooting the system some tool complained about misconfigured ssh equivalence. So i digged a little bit. I found out SSH is complaining about wrong directory permissions:

Sep 28 13:57:03 rac1 sshd[31620]: Authentication refused: bad ownership or modes for directory /u01/app/oracle/product/11.2.0/ora11p

The directory mentioned here is an ACFS shared oracle home and the home directory for the oracle user. After changing the mode for the directory to 755 ssh equivalence was restored. But after stopping and starting acfs resource the equivalence was gone again.

So i worked a little bit on that:

Lets first check directory permission with ACFS resource not started and not mounted:

[root@rac1 ~]# ll /u01/app/oracle/product/11.2.0/
total 4
drwxr-xr-x 2 ora11p dba 4096 Sep 13 00:02 ora11p
[root@rac1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              26G   13G   12G  52% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 1.9G  164M  1.7G   9% /dev/shm

Directory Mode is 775.

So now lets mount ACFS volume manually and check the permission again:

[root@rac1 ~]# mount /dev/asm/ora11p_home-132 /u01/app/oracle/product/11.2.0/ora11p/ -t acfs
[root@rac1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              26G   13G   12G  52% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 1.9G  164M  1.7G   9% /dev/shm
/dev/asm/ora11p_home-132
 10G  4.7G  5.4G  47% /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]# ll /u01/app/oracle/product/11.2.0/
total 16
drwxrwx--- 83 ora11p dba 12288 Sep 25 10:37 ora11p

775 – still no surprise. So we change them to 775 as required by SSH:

[root@rac1 ~]# chmod 755 /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]# ll /u01/app/oracle/product/11.2.0/
total 16
drwxr-xr-x 83 ora11p dba 12288 Sep 25 10:37 ora11p

The directory show required permissions. We will now unmount and mount the file system again:

[root@rac1 ~]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda3             26306612  12828996  12119724  52% /
/dev/sda1               101086     11683     84184  13% /boot
tmpfs                  1933304    167016   1766288   9% /dev/shm
/dev/asm/ora11p_home-132
 10485760   4864328   5621432  47% /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]# umount /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]#
[root@rac1 ~]# umount /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]# mount /dev/asm/ora11p_home-132 /u01/app/oracle/product/11.2.0/ora11p/ -t acfs           
[root@rac1 ~]# ll /u01/app/oracle/product/11.2.0/
total 16
drwxr-xr-x 83 ora11p dba 12288 Sep 25 10:37 ora11p

There we are: Permission mode 775 is consistent accross mounts. So lets unmount everything and start acfs resource again:

[root@rac1 ~]# umount /u01/app/oracle/product/11.2.0/ora11p
[root@rac1 ~]#
[root@rac1 ~]# /u01/app/11.2.0/grid/bin/crsctl start resource  ora.data2.ora11p_home.acfs
CRS-2672: Attempting to start 'ora.data2.ora11p_home.acfs' on 'rac1'
CRS-2672: Attempting to start 'ora.data2.ora11p_home.acfs' on 'rac2'
CRS-2676: Start of 'ora.data2.ora11p_home.acfs' on 'rac2' succeeded
CRS-2676: Start of 'ora.data2.ora11p_home.acfs' on 'rac1' succeeded
[root@rac1 ~]# ll /u01/app/oracle/product/11.2.0/
total 16
drwxrwx--- 83 ora11p dba 12288 Sep 25 10:37 ora11p

The directory mode 770 was changed to 770…. but by which component and configuration?

Until now i did not find a solution for this behavior yet. I will open a SR and see what Oracle thinks about this “feature”.

In the meantime to get rid of this behavior you can set “StrictModes no” in sshd_config to prevent ssh from checking directory ownerships.

System configuration

Hardware configuration

• two virtual machines (VMWARE)
  • 1 vCPU
  • 4 GB RAM
  • 40 GB local Disk
• Storage exported via ISCSI
  • 4 LUNs with 10 GB each
  • 2 LUNs with 30 GB each

Operating system configuration

• Oracle Enterprise Linux 5.3 x86_64 (Kernel 2.6.18-128.el5)
• Installed packages: default system + development packages

Cluster configuration

• Cluster Name: „RAC“
• Grid Binary installation on local disk
• OCR, Voting and datafiles stored in ASM
• Oracle HOME stored on ACFS file system (this menas we will have a SHARED home directory among all nodes!)
• Oracle HOME will be installed unser user „ora11p“

Installation – Requirements and Preparations

Installation Steps outlined

1. Installation of Oracle 11g Release 2 Grid Infrastructure → done here
2. Installation of Oracle 11g Release 2 Database (rac installation)
   1. Review system requirements
   2. Install database software (aka „binaries“)
   3. Create database

general Requirements

All requirments from grid infrastructure installation apply here as well, for instance:

• Kernel parameter
• Limits (esp. configure limits for new user „ora11p“ which will hold the binary database installation)
• Synchronous time
• dns-resolvable SCAN name
• working public and private interconnect
• shared and accessible storage
• at least ONE better two more disk groups created:
  • one for database files and binary installation
  • one for flashback recovery area
• Note: SSH equivalence will be set up by installer

Preparations

Create ACFS file system for storing oracle binary installation

• Create further ACFS mount directory

  mkdir -p /u01/app/oracle/product/11.2.0/ora11p

• Create ADVM volume

• Create ACFS file system

• DO NOT register ACFS file system mountpoint for the oracle home directory! We will do this later (when creating the database) as clusterware resource

• Mount ACFS file system on both nodes ( “mount /dev/asm/ora11p_home-132 /u01/app/oracle/product/11.2.0/ora11p”)

 

Create User on both nodes:

useradd -u 501 -g dba -d /u01/app/oracle/product/11.2.0/ora11p ora11p
passwd ora11p
chown -R root:dba /u01/app/oracle/product
chmod -R 775 /u01/app/oracle/product
chown -R ora11p:dba /u01/app/oracle/product/11.2.0/ora11p

Create .bash_profile for user ora11p (note: changes on node A will be visible on node B cause were using ACFS; so changing profile file is needed only once)

export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/ora11p
export ORACLE_SID=ORA11P
if [ -t 0 ]; then
stty intr ^C
fi

One word on Cluster Verification utility (cluvfy)

• should be used prior installation
• At this point the user „ora11p“ does not have SSH equivalence configured
• So there are two options:
  • start cluvfy after installer set up ssh equivanlence
  • set up SSH equivalence manually
• I personally prefer to run cluvfy after installer set up ssh equivalence

However the database installer seems to run a more or less complete check automatically

If you want to start cluvfy here is the syntax:

cluvfy stage -pre dbinst -fixup -n nodeA,nodeB -r <release> -osdba <name of sysdba group on unix> -verbose
<release> is: 10gR1, 10gR2, 11gR1, 11gR2

Installation

Start installer als user „ora11p“ on any node

For testing purposes i deselected update notifications… in productive environments this is highly recommended

we will install database software only and create database later

both nodes were discovered correctly….

Because were installing as user „ora11p“ which is different from the user holding our infrastructure installation we need to create passwordless ssh connectitivty

!! you also need to select „user home is shared“ cause were using ACFS !!

SSH connectivity successfully established…

Select language support

Select Edition

Select Options

Select ORACLE_BASE and ORACLE_HOME; we set it in profile file so it is entered by the installer automatically

Installation Summary

Install process

Installation nearly finished.. just start „root.sh“ as root on all nodes

root.sh sample output

Finished

Where to go now?

• We just installed all neccessary components for creating our first RAC database → this will be the next post
• backup current configuration