Blog Archives

Physical vs Logical Blocksize on ASMLib Devices

As you all may know, ASMLib is a recommended module for Oracle databases running on Linux platforms and it is an embedded module for UEK (Oracle Unbreakable Kernel) users. Oracle announced that (two years ago or so) they will no longer maintain ASMLib for Red Hat compatible kernel but this does not mean that they abandon the project, rather it is mainly related to the effort they need to put in maintaining the module for multiple kernel versions.

A while ago, Oracle added a new feature to ASMLib allowing ASM devices to choose between physical or logical block sizes in I/O operations. This should be, I believe, a fail-back mechanism for SSD devices used as ASM disks. Many SSD devices use 4K block size however Linux still uses default 512 bytes logical block size for those devices in the same way it does for motor disks. In early releases of ASMLib (oracleasm-support-2.1.7 and earlier), ASM uses physical block size (4K for SSDs). This is still the default behavior in oracleasm-support-2.1.8 but now sysadmin can choose between physical and logical blocksize by using [-b|-p] switches in script.

  • -b|—logical-blocks sets logical blocksize usage
  • -p|—physical-blocks set physical blocksize usage

Those switches set /sys/module/oracleasm/parameters/use_logical_block_size which is default to be false (use physical blocksize). So that asmlib module can use the value to decide which block size to use.

How to Install Oracle 11g Release 2 on OEL 5.4 on VirtualBox: Managing ASM with ASMCA

In the previous post, I have tried to explain how to install Grid Infrastructure on your VirtualBox instance. In this post, before moving to the next post in which I will be explaining RDBMS 11g Release 2 configuration, I wish to look at a new tool shipped with Grid Infrastructure, namely ASMCA(ASM Configuration Assistant).

We will not be going deep with ASMCA in this post but rather it will be just like a first contact with aliens. ASMCA is a very capable and accompanying tool with the new capabilities of ASM like ADVM or ACFS.

Starting with ASMCA

init Starting ASMCA is simple. Go to your GRID_HOME set ORACLE_SID to +ASM and run asmca binary.

[oracle@localhost ~]$ export ORACLE_HOME =/u01/app/oracle/product/11.2.0/grid
[oracle@localhost ~]$ export ORACLE_SID = +ASM
[oracle@localhost ~]$ $ORACLE_HOME/bin/asmca

As you will notice there is already one disk group namely DATA listed under Disk Gruops pane. This is the one created during Grid Infrastructure installation.
Now click on Create to create our FRA diskgroup.

creatediskgroup As you click on Create button a new dialog to create your new disk group will appear. 
Enter FRA for Disk Group Name textbox.
Choose External(None) radio button to choose external ASM redundancy.
Notice that not all disks (asm disks) are available for your use (this controlled by two radio buttons in Select Member Disks pane) Select all three disks for FRA.
Now click on Show Advanced Options button to see RDBMS and ASM compatibilities.
advancedoptions Notice that ASM and Database Compatibility fields are both set to
This means ASM instance will allow you to use all new features introduced in 11.2 for this diskgroup but the minimum RDMS instance can use this diskgroup should be in 11.2 release.
Click on Hide Advance Options button and then OK to complete diskgroup creation.
creatediskgroup2 ASM will do the necessary initializations to create FRA diskgroup and switch back to initial screen after it is done.
rightclickondiskgruop As you see FRA is created and mounted by your ASM instance.
rightclickonDATA Now right click on your DATA diskgroup. In the list ASMCA allows you to

  • Add Disks into the diskgroup
  • Edit Attributes of the diskgroup
  • Manage Templates for the diskgroup
  • Mount/Dismount the diskgroup
  • Drop the diskgroup

Choose Edit Attributes from the list to see attributes of DATA diskgroup.

diskgroupProperties As you see ASMCA enables the attribute fields those are possible to modify and disables the static ones (the ones fixed in creation of diskgroup).
Click X to close this window.
exit Click on Exit button to leave ASMCA.

ASMCA is the youngest member of Oracle *CA family. It seems that ASM users will be using it actively for management by the new features in 11g Release 2. Such as,

  • ASM Volume (ADVM) Management
  • ASM File System (ACFS) Management
  • Read-only snapshot management

How to Install Oracle 11g Release 2 on OEL 5.4 on VirtualBox: Installing Grid Infrastructure

In Oracle 11g Release 2 you will find that things have changed even for single instance database installation. I will try to illustrate in this series of posts how to install a single instance Oracle 11g Release 2 database to your Linux machines.

As the first part of our installation series, we will start by installing brand new Grid Infrastructure which you might think to be a fancy name for CRS+ASM but you will find out later that it is a bit more.

VirtualBox Configuration

Here is the sufficient VirtualBox virtual hardware configuration for your 11g Release 2 playground (Keep in mind that this is the bare minimum configuration to have a painless installation. More resource is obviously better):

Hardware Amount Description
Memory 512MB Although minimum memory requirement for Oracle 11g Release 2 in a real production environment is documented to be 1024M, for all practical requirements of your playground 512MB will be sufficient.
Root Disk 16GB 16 GB root disk for OS+SWAP+Oracle Binary space will be sufficient
ASM Disks 6x2GB SCSI Disks Oracle 11g Release 2 Beta 2 AyarlarWe will be doing an ASM based installation so 6 disks over SCSI interface will be enough to simulate a real life experience with ASM.

You are now ready to start your VirtualBox for Oracle 11g Release 2 installation.

Install Grid Infrastructure


There are a few important tasks in OS level we should complete before starting grid infrastructure installation.

Physical Partition Creation

The first thing is to create physical partitions over your virtual SCSI devices. Actually this is not crucial for ASM installation because ASM can use physical disk as a whole without any partition. However if you wish to create ASMLIB you will need those partitions.

[root@localhost ~]# fdisk /dev/sda
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won’t be recoverable.Warning: invalid flag 0x0000 of partition table will be corrected by w(rite)Command (m for help): n
Command action
e     extended
p     primary partition (1-4)
Partition number (1-4): 1
First cylinder (1-261, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-261, default 261):
Using default value 261Command (m for help): w
The partition table has been altered!


Calling ioctl() to re-read partition table.
Synching disks.

Changing ASM devices ownership to oracle

Physical partitions we have created are owned by root. They should be changed to be owned by ASM user (oracle in our case) in order to make them visible for ASM discovery.

[root@localhost ~]# lsla /dev/sd?1
brw-r—– 1 root disk 8,  1 Sep 21 05:03 /dev/sda1
brw-r—– 1 root disk 8, 17 Sep 21 05:03 /dev/sdb1
brw-r—– 1 root disk 8, 33 Sep 21 05:03 /dev/sdc1
brw-r—– 1 root disk 8, 49 Sep 21 05:03 /dev/sdd1
brw-r—– 1 root disk 8, 65 Sep 21 05:03 /dev/sde1
brw-r—– 1 root disk 8, 81 Sep 21 05:03 /dev/sdf1[root@localhost ~]# chown oracle:dba /dev/sd?1[root@localhost ~]# ls –la /dev/sd?1
brw-r—– 1 oracle dba 8,  1 Sep 21 05:03 /dev/sda1
brw-r—– 1 oracle dba 8, 17 Sep 21 05:03 /dev/sdb1
brw-r—– 1 oracle dba 8, 33 Sep 21 05:03 /dev/sdc1
brw-r—– 1 oracle dba 8, 49 Sep 21 05:03 /dev/sdd1
brw-r—– 1 oracle dba 8, 65 Sep 21 05:03 /dev/sde1
brw-r—– 1 oracle dba 8, 81 Sep 21 05:03 /dev/sdf1

In order to make those changes permanent (if you reboot the system Linux will set all device owners back to root otherwise) you should create a udev permission file

[root@localhost ~]# more /etc/udev/rules.d/99-oracle.rules
#ASM disks
KERNEL==”sda”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″
KERNEL==”sdb”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″
KERNEL==”sdc”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″
KERNEL==”sdd”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″
KERNEL==”sde”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″
KERNEL==”sdf”, OWNER=”oracle”, GROUP=”dba”, MODE=”0660″

Ensure /dev/shm is sufficiently sized

You should ensure that /dev/shm is minimum 256MB for a successful ASM installation (and 512-750M for RDBMS installation) with MEMORY_TARGET parameter.

[root@localhost ~]# dfha
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00 15G 9.9G 3.9G 72% /
proc 0 0 0 /proc
sysfs 0 0 0 /sys
devpts 0 0 0 /dev/pts
/dev/hda1 99M 32M 63M 34% /boot
tempfs 125M 0 125M 0% /dev/shm
none 0 0 0 /proc/sys/fs/binfmt_misc
sunrpc 0 0 0 /var/lib/nfs/rpc_pipefs
oracleasmfs 0 0 0 /dev/oracleasm

You can resize tempfs online by using

[root@localhost ~]# mount /dev/shm –o size=750M,remount

In order to make this mount operation persistent you should modify the tempfs line in /etc/fstab file as follows:

[root@localhost ~]# cat /etc/fstab | grep tempfs
tmpfs                   /dev/shm                tmpfs   size=750m        0 0

Notice that although we have VirtualBox instance with 512M memory, Linux allows us to mount tempfs with a size of 750M. This most probably due to lazy allocation of memory over tempfs.

Create installation directory and set its ownership

Final step is to create our software directory and set the required ownership to it.

[root@localhost ~]# mkdir -p /u01/app
[root@localhost ~]# chown -R oracle:oinstall /u01/app/oracle


Camtasia Studio (5)
[oracle@localhost ~]$ unzip
[oracle@localhost ~]$ cd grid
[oracle@localhost grid]$ ./runInstaller
Camtasia Studio (7) Choose Install and Configure Grid Infrastructure for a Standalone Server option and click on Next > button.
Camtasia Studio (14) Set Selected Language language to English and click on Next > button.
Camtasia Studio (9) Next step is to perform ASM configuration for your grid. Choose External as the redundancy of DATA diskgroup. Now click on Change Discovery Path… button to define asm_diskstring parameter.
Camtasia Studio (15) Set Disk Discovery Path to /dev/sd?1 and click on OK
Camtasia Studio (16) Since /dev/sd?1 matches all six SCSI partitions and they are not members of any other diskgroup, installer will list all of them as Candidate disks.Check-out /dev/sda1,/dev/sdb1,/dev/sdc1 devices as members disks of DATA diskgroup then click on Next >Other disks will be used for Flash Recovery Area later on.
Camtasia Studio (17) Choose Use same passwords for these account for a simple configuration then set Specify Password and Confirm Password fields to same password strings and click on Next >.I will be using sysadm throughout the post for any Oracle password required.
Camtasia Studio (18) One of the security enhancements introduced in Release 2 is the separation of different levels of ASM access. This defines different roles for “Who can start/stop ASM instance ?”, “Who can add/drop disks to/from diskgroups?” or “Who can use those diskgroups at RDBMS level ?”For the simplicity of installation we will be setting all roles to dba group.Now set all three select lists to dba and click on Next >.
Camtasia Studio (52) Set Oracle Base to /u01/app/oracle and Software Location to /u01/app/oracle/product/11.2.0/grid. Then click on Next >.
Camtasia Studio (22) Next step is unique to first Oracle software installation as you all may know. You should set Inventory Directory (if it is not already set by installer) to /u01/app/oraInventory. Keep oraInventory Group Name as oinstall and click on Next >
Camtasia Studio (23) In this step installer will check the installation prerequisites as it does in previous releases.
Camtasia Studio (26) By 11g Release 2, if any of the prerequisites fail it will be reported in a tree structure with different categories. In my case majority of the kernel settings are automatically managed since I have installed oracle-validated-configuration rpm during OEL installation.Only problem seems to be insufficiently sized which is defined to be the maximum socket send buffer size.When you click on Fix & Check Again button, installer will generate a single shell script for you to correct all fixable errors and after its execution it will recheck for any possible problems left.
Camtasia Studio (27) Run the generated script as root user

[root@localhost ~]# /tmp/CVU_11.
Response file being used is :/tmp/CVU_11.
Enable file being used is :/tmp/CVU_11.
Log file location: /tmp/CVU_11.
Setting Kernel Parameters…
net.core.wmem_max = 262144
net.core.wmem_max = 1048576

When the script is executed click OK to restart the prerequisite check process.

Camtasia Studio (31) As you see kernel parameter problem has gone. Other three errors can not be corrected by installer automatically, but we know that those are not critical ones. First one is PhysicalMemory error due to our VirtualBox 512 MB memory size. The second one is insufficient SwapSize that can be by-passed also for a play ground. And the final problem is RunLevel of Linux which is also not a great deal for us.Now check Ignore All and click on Next > (button will be enabled after checking out Ignore All) to continue.
Camtasia Studio (32) On the summary screen confirm that everything is ok and click on Finish to start installation.
Camtasia Studio (35) After installer successfully completes copy,install,link,etc steps it will pop-up a execution dialog. Run the required scripts as root.

[root@localhost ~]# /u01/app/oraInventory/
[root@localhost ~]# /u01/app/oracle/product/11.2.0/grid/

Then switch back to installation dialog and click OK in Execute Configuration scripts dialog to proceed.

Camtasia Studio (45) Final tasks for installer will be to configure new HA service for ASM, diskgroup (DATA) and the default listener (on port 1521) which will be automatically configured also .
Camtasia Studio (48) Finally we are done 🙂 Your ASM, default listener, and HA service is ready to be used.

Post Installation Checks

Login ASM

[oracle@localhost ~]$ export ORACLE_HOME = /u01/app/oracle/product/11.2.0/grid [oracle@localhost ~]$ export ORACLE_SID = +ASM
[oracle@localhost ~]$ export PATH = $ORACLE_HOME/bin:$PATH
[oracle@localhost ~]$ sqlplus / as sysasm
SQL*Plus: Release Beta on Mon Sep 21 05:45:58 2009 Copyright © 1982, 2009, Oracle. All right reserved. Connected to:
Oracle Database 11g Enterprise Edition Release – Beta
With the Automatic Storage Management option


SQL> select name from v$asm_diskgroup;


Check Default Listener Status

[oracle@localhost ~]$ lsnrctl status LSNRCTL for Linux: Version – Production on 31-OCT-2009 12:05:36 Copyright (c) 1991, 2009, Oracle.  All rights reserved. Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version – Production
Start Date                31-OCT-2009 11:51:00
Uptime                    0 days 0 hr. 14 min. 37 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/11.2.0/grid/network/admin/listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/localhost/listener/alert/log.xml
Listening Endpoints Summary…
Services Summary…
Service “+ASM” has 1 instance(s).
Instance “+ASM”, status READY, has 1 handler(s) for this service…
The command completed successfully

Check HA Targets

[oracle@localhost ~]$ crs_stat -t
Name           Type           Target    State     Host
ora.DATA.dg    ora….up.type ONLINE    ONLINE    localhost
ora….ER.lsnr ora….er.type ONLINE    ONLINE    localhost
ora.asm        ora.asm.type   ONLINE    ONLINE    localhost
ora.cssd       ora.cssd.type  ONLINE    ONLINE    localhost
ora.diskmon    ora….on.type ONLINE    ONLINE    localhost

“How to Achieve All in One with Oracle 11g” Material

Here is the content of my first presentation in Open World 2009:

How to Achieve All in One with Oracle 11g

SQLAlchemy for Oracle ORM in Python

smilingpythonHi there,

I am trying to learn Python for some daily scripting activities on Oracle databases. I hope you all familiar with ORM tools available for other programming languages. I have already found a very developer friendly ORM tool for Python called SQLAlchemy. In this post you will find a basic usage of this tool to write better Oracle-Python codes. We will be going through the answer of a simple question:

How to compute an ASM Diskgroup Read Rate?

with my special thanks to Anil Chalil…