DBFS on Oracle Exadata

Follow below steps to create DBFS

Create the mount point for DBFS

[root@db01 ]# mkdir /dbfs_dir

Login with Oracle user

[root@db1 ]# su - oracle

Set the Oracle Database environment variable to connect the your database.

Connect Database as sysdba

[oracle@db01 ~]$ sqlplus  / as sysdba

Create tablespace on ASM disk group

SQL> create tablespace dbfsts datafile '+DATA' size 1G;

SQL> create user dbfs_usr identified by Dbfs_pwd1 default tablespace dbfsts quota unlimited on dbfsts;

SQL> grant create session, create table, create procedure, dbfs_role to dbfs_usr;

You can use below syntax to create bigfile tablespace.

create bigfile tablespace dbfsts datafile '+DATA' size 2048g autoextend off nologging extent management local;

Go to admin directory of oracle binaryand run the below procedure

$cd $ORACLE_HOME/rdbms/admin

$sqlplus dbfs_usr/Dbfs_pwd1

SQL> start dbfs_create_filesystem_advanced dbfsts FS nocompress nodeduplicate noencrypt non-partition

Above procedure should run without errors.


[oracle@db01 ~]$ echo Dbfs_pwd1 > pwd.txt

[oracle@db01 ~]$ nohup $ORACLE_HOME/bin/dbfs_client dbfs_usr@test /dbfs_dir < pwd.txt &

- 'test' is database name
- '&' to run the process in background
- '/dbfs_dir' is a directory on which DBFS will be mounted

LOGIN to Oracle USER account from another terminal and check the DBFS file system

[oracle@db01 ~]$ cd /dbfs_dir/FS
[oracle@db01 ~]$ touch test.txt
[oracle@db01 ~]$ ls -ltr test.txt

LOGIN to root USER account from another terminal and check whether you can get acces of the DBFS file system

[root@db01 ]# cd /dbfs_dir/FS
Permission Denied

To unmount the file system issue the following command from the "root" OS user.

[root@db01 ]# fusermount -u /dbfs_dir

To allow other users ( example root to access the filesystem )

[oracle@dbs1 ]$ su - root
Password :

[root@db01 ]# echo user_allow_other > /etc/fuse.conf

change permission of /etc/fuse.conf to 644

[root@db01 ]#chmod 644 /etc/fuse.conf

[root@db01 ]# su - oracle

[oracle@db01 ~]$ nohup $ORACLE_HOME/bin/dbfs_client dbfs_usr@test -o direct_io,allow_root /dbfs_dir < pwd.txt &

You can check nohup file for any error logs.

Login to root user account from another terminal and check the accessibility of DBFS

[root@db01 ]# cd /dbfs_dir/FS
[root@db01 ]# ls -lt test.txt

To unmount the file system issue the following command from the "root" OS user.

# fusermount -u /dbfs_dir

User Equivalence between DB Node and Storage Cell

In configuration of user equivalence is quite simple as it has been managed by executable script which doesn't required manual actions which generally we do in normal server setup.

Explained user equivalence setup procedure for Exadata servers and storage.

Checking the hostname on storage server from DB node with dcli utility where SSH equivalence has not been configured.

[oracle@ex01dbm01 ~]$ dcli -c ex01cel01 -l oracle hostname
celladmin@ex01cel01's password:
ex01cel01: ex01cel01@example.com

Now pushing SSH key to storage cell with below command

[oracle@ex01dbm01 ~]$ dcli -g ./cell_group -k
celladmin@ex01cel02's password:
celladmin@ex01cel01's password:
celladmin@ex01cel03's password:
ex01cel01: ssh key added
ex01cel02: ssh key added
ex01cel03: ssh key added

Here cell_group is the list of cell storage server name .

Now executing dcli on storage cell to check whether user equivalence has been configured properly or not.

[oracle@ex01dbm01 ~]$ dcli -c ex01cel01 -l oracle hostname
ex01cel01: ex01cel01@example.com

Above command has not asked any password to login into the cel01 that means equivalence is working fine.

                            Oracle User Equivalence between two DB servers


Exadata Monitoring Tools

Many requests came that how we can monitoring Exadata and what are the monitoring tolls available so listed known Exadata monitoring tools as well as configuration check tool.

Exacheck -- To check whether Exadata configuration has been done as per best practice or not.

OSWatcher -- It monitors server resources and gives past resource consumption details if required.

OEM (Oracle Enterprise Manager) -- It used to monitor Exadata end to end. With OEM we can monitor each and every components of Exadata. It is useful to monitor Hardware as well as software.

ASR (Auto Service Request) -- It is used to monitor Exadata hardware. Automatically it creates service request in oracle support.

We will explain each tool with setup & configuration in separate post.

                               Exadata Machine Monitoring Commands

How to Verify Hardware and Firmware on Exadata Components (Storage & Server) ?

If the hardware and firmware are not validated, inconsistencies between database and storage servers can lead to problems and outages.

With below command we can verify hardware and firmware on storage and server.

# /opt/oracle.cellos/CheckHWnFWProfile

[SUCCESS] The hardware and firmware profile matches one of the supported profile

If any result other than "SUCCESS" is returned, investigate and correct the condition.

Hot to Verify InfiniBand Fabric Topology ?

Verifying infiniband topology whether it is configured current or not. If it not gives the desired output as per below then it will cause the InfiniBand network to operate at degraded efficiency, intermittently, or fail to operate.

# /opt/oracle.SupportTools/ibdiagtools/verify-topology -t fattree

[ DB Machine InfiniBand Cabling Topology Verification Tool ]
Is every external switch connected to every internal switch..........[SUCCESS]
Are any external switches connected to each other....................[SUCCESS]
Are any hosts connected to spine switch..............................[SUCCESS]
Check if all hosts have 2 CAs to different switches..................[SUCCESS]
Leaf switch check: cardinality and even distribution.................[SUCCESS]
Check if each rack has an valid internal ring........................[SUCCESS]

If anything other than "SUCCESS" is reported, investigate and correct the condition.

Exadata Hybrid Columnar Compression (EHCC)

Let's see how EHCC help us to reduce storage space with performance database improvement.

Here we have created three tables with same data as per below.

1. Test  with no compression
2. Test_hcc_archive with archive high compression
3. Test_hcc_query with query high compression

#### List of tables with compression types ####

SQL> select table_name,compression,compress_for
  2    from user_tables
  3   where table_name in ('TEST','TEST_HCC_QUERY','TEST_HCC_ARCHIVE');

TABLE_NAME                 COMPRESS COMPRESS_FOR                            
------------------------------ -------- ------------                            
TEST                           DISABLED                                         
TEST_HCC_ARCHIVE      ENABLED    ARCHIVE HIGH                            
TEST_HCC_QUERY         ENABLED    QUERY HIGH                              

#### Each Tables are with 100000 row data ####

SQL> select count(*) from test;


Elapsed: 00:00:00.11

SQL> select count(*) from test_hcc_query;


Elapsed: 00:00:00.10

SQL> select count(*) from test_hcc_archive;


Elapsed: 00:00:00.10

#### Checking the size of data for each tables ####

Exadata Interview Questions Part -2

Get an e-book of Exadata Interview Questions and Answers to stay miles ahead of your competition..!!!

  • What is cell disk ?
  • What is grid disk ?
  • What is IORM ?
  • What are the ways to migrate on Exadata ?
  • Procedure to drop cell disk on Exadata.
  • What is cellsrv and how it works ?
  • Use of cellsrv service on Exadata storage cell.
  • What is iDB protocol ?
  • What is the purpose to use Exacheck tool ?
  • What is the oswatcher and how it works ?
  • What is RS services and how it works ?
  • How to enable HCC on database table ?
  • How many networks are available on Exadata ?
  • How we can integrate OEM12c with Exadata ?
  • What are the ways to install OEM12c agent on Exadata ?
  • Which cell services are running on Exadata storage cell ?
  • Purpose of MS(management service) on storage cell.
  • How cell storage software backup happens ?
  • Which OS supports by Exadata ?
  • How to power off Exadata Machine ?
  • How to do maintainance on Cell Storage and DB server?
  • What is writet-through caching mode ?
  • What is Write-back caching mode ?
  • Explain the procedure to drop the Cell storage ?
  • How to replace physical storage disk on cell storage ?
Get Questions and Answers HERE.....

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How to find and delete older files with bigger size files in Linux

To find out files size more than 5MB

#find . -size +5000  -exec ls -ltr {} \; 

 To **Remove** files size more than 5MB

#find . -size +5000k  -exec rm -rf {} \;

To find out files older than 30days

#find . -mtime +30 -exec ls -ltr {} \;

To find **Remove** files older than 30days

#find . -mtime +30  -exec rm -rf {} \; &

                                  Linux Server Performance Analyzer Tools

OEM11g / OMS Auto Start and Stop Script for Linux

After installation OEM 11g mostly we required is to start the OEM services even after server reboot so here you will see how to make a OEM start-up script and add into the OS start-up sequence.

This is purely to avoid manual operation of OEM start-up if in any case we reboot the server.

1. Create dbora (service name) file as below: 

 vi /etc/init.d/dbora

#Run-level Startup script for the Oracle Instance and Listener

# chkconfig: 345 91 19
# description: Startup/Shutdown Oracle listener and instance



# if the executables do not exist -- display error

Power Off Sequence for Exadata Stack

Poweroff Database Servers

For single server power off /Restart

1. First stop the oracle cluster with below command

#$GRID_HOME/grid/bin/crsctl stop cluster

2. If it fails to stop the cluster then use -f option to stop it forcefully.
Shutdown the server with below command

#shutdown -h -y now

To restart the server execute below command

#shutdown -r -y now      or      #reboot

3. Remove power cable from the server

For multiple servers poweroff/restart with dcli utility

1. First stop the oracle cluster with below command

#$GRID_HOME/grid/bin/crsctl stop cluster -all

2. Shutdown all the servers with dcli utility

#dcli -g dbs_group -l root shutdown -h -y now

---dbs_group is the file which contains the list of all the exadata servers.

To restart the server execute below command

#dcli -g dbs_group -l root shutdown -r -y now    or  #dcli -g dbs_group -l root reboot

----dbs_group is the file which contains the list of all the exadata servers.

3. Remove power cables from the servers

Poweroff Storage Servers

Reat the same procedure of server to power off the exadata storage servers except to stopping the crsctl.

Note: We have to use cell_group file instead of dbs_group file to shutdown the storage servers.

Poweroff Network Equipments

We can directly remove power cables from the network switches as network equipments don't have power switches.

How to find serial number of Exadata Server/Storage

Execute below command on operating system to find the serial number of DB node and Storage cell.

# ipmitool sunoem cli "show /SP system_identifier"


[root@db01 ~]#  ipmitool sunoem cli "show /SP system_identifier"

Connected. Use ^D to exit.
-> show /SP system_identifier


        system_identifier = Exadata Database Machine X3-2 AK00097035

-> Session closed


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Exadata Storage Server Shutdown/Startup procedure

Shutdown Procedure

1. Execute below command to check if there is any offline disk    

cellcli > list griddisk attributes name where asmdeactivationoutcome != ‘ yes’

if it write anything then it's not safe to offline the storage server as disk redundancy will not maintained properly.

2. Inactivate all the griddisk with below command if step one positively executed with no output

Cellcli > alter griddisk all inactive

3. Verify whether all disks are inactive or not with below command

Cellcli > list griddisk where status =! ‘inactive’

If all disk grid disks are inactive then we can proceed to shutdown the storage server.

Startup Procedure

1. Start the cell. All cell services will come up automatically.

2. Bring all disk online

Cellcli > alter griddisk all active

3. Verify whether disks successfully came online or not

Cellcli > list griddisk attributes name, asmmodestatus

All disks should come online. If any of the disk is not online then wait sometimes to change the disk status.

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