Oracle ASM
supports creation of a traditional file system on top of an ASM disk group. This
file system is accessible to applications once mounted, and it supports all
kinds of application files, and has been known as ACFS.
The ACFS
file system has a storage snapshot feature. A storage snapshot is an image of a file
system as it existed at some point in time. Storage snapshots are fast and
efficient because they do not consume disk space or resources at creation time.
They can be created as read-only or read-write snapshots.
Only when
the file system contents are updated, do the ACFS drivers work to maintain the snapshot.
This is
called copy-on-write technology, and enables the initial duplication of large
file systems with little effort.
Starting
version 12.1, ACFS supports storage of database datafiles in the Grid
Infrastructure environment.
In this
doc, we will create a container database on top of an ACFS file system first.
Next, we
will use the ACFS storage snapshot feature to rapidly duplicate one of the tenant
databases.
We will use
the STORAGE SNAPSHOT capability of the CREATE PLUGGABLE DATABASE statement.
The requirement for use of STORAGE SNAPSHOT clause is that the source pdb datafiles be stored on a system which supports storage snapshots.
When we duplicate an existing pluggable database specifying the storage
snapshot argument, ACFS drivers automatically create a read-write storage snapshot,
and maintain it.
Duplicating
an existing database otherwise requires copying of the source datafiles to the
new destination which can take a long time, and a lot of storage if the
database is large.
The
exercise will progress in stages.
Stage
# 1 – Linux and Oracle Restart install
The ASM
storage will use a single external redundancy disk, exposed to ASM as an asmlib
disk. We take care to inspect the new disk group’s attributes, and make sure that
COMPATIBLE.ADVM is set to 12.1 at least.
Though
not supported, this example uses Oracle Restart for establishing the ASM
environment, for testing purposes.
Stage
# 2 - Creation of the asm dynamic volume and asm cluster file system.
We will
use the asm cluster file system to store the database datafiles.
Note that
this is only a test, and in fact, storing of database datafiles on ACFS is NOT supported for Oracle Restart.
Oracle 12.1
only supports database datafile storage on ACFS for Grid Infrastructure.
Stage
# 3 – Creation of a test database on the file system
We will
create a test database called CDB2 containing a single PDB called TOOLS.
Stage
# 4 – PDB duplication using the storage snapshot feature.
The PDB
named TOOLS will be duplicated using the storage snapshot option of the CREATE
PLUGGABLE DATABASE command.
Stage
# 1 – Linux and Oracle Restart install
# Set up asmlib by installing the oracle asmlib rpms.
Next, we identify
the unix kernel and download the correct kernel-specific asmlib driver files as
recommended by oracle asmlib download site.
[oracle@linux12c CDB2]$ uname -r
2.6.18-308.el5
These are
the asmlib listed for the above unix kernel
oracleasm-2.6.18-308.el5-2.0.5-1.el5.x86_64.rpm
oracleasm-support-2.1.8-1.el5.x86_64.rpm
oracleasmlib-2.0.4-1.el5.x86_64.rpm
For this example, a single 6 GB asmlib disk named DISK1 is configured before Oracle Restart install.
[oracle@linux12c CDB2]$ /usr/sbin/oracleasm listdisks
DISK1
#Set up Oracle Restart and configure GI for Oracle
Restart
After
configuring the grid and oracle users and the groups asmadmin, asmdba, and
oinstall, the Grid Infrastructure installer GUI can be started. Using the OUI,
and running as the grid user, the option to install and configure grid
infrastructure for standalone environment was selected, and the Oracle Restart environment was created.
# Start up acfs drivers manually as
shown (need to do it each boot for Oracle Restart env)
The drivers
will be loaded up as part of Oracle Restart install, but will not be started
automatically on boot.
If
required, start up the drivers using the acfsload executable found in the grid
home under the bin folder, as shown.
root@linux12c ~]#
/u01/app/grid/product/12.1.0/grid/bin/acfsload start -s
ACFS-9391: Checking for existing ADVM/ACFS installation.
ACFS-9392: Validating ADVM/ACFS installation files for
operating system.
ACFS-9393: Verifying ASM Administrator setup.
ACFS-9308: Loading installed ADVM/ACFS drivers.
ACFS-9154: Loading 'oracleoks.ko' driver.
ACFS-9154: Loading 'oracleadvm.ko' driver.
ACFS-9154: Loading 'oracleacfs.ko' driver.
ACFS-9327: Verifying ADVM/ACFS devices.
ACFS-9156: Detecting control device
'/dev/asm/.asm_ctl_spec'.
ACFS-9156: Detecting control device '/dev/ofsctl'.
ACFS-9322: completed
To check
if drivers are loaded, run lsmod | grep oracle
as the root.
This completes the os
and software set up stage.
Stage
# 2 - Creation of the asm dynamic volume and asm cluster file system.
First an
ASM volume called VOL1 with 6GB space was carved out of the asm disk group
DATA. The screenshot below shows the details of the ADVM volume. This volume
will be exposed to the os as a device file, in this case it's name and path is /dev/asm/vol1-181.
Next, we
create an ACFS file system on top of this volume device. The following ACFS
file system was created using asmca as shown. ASMCA has also created a mount point for the new
file system.
# Mount the acfs file system as the root user.
The next
step is to mount the file system so that applications can access it. (Additionally,
create a folder called oradata under the mount point, and give read/write
permissions to the oracle user so that database files can be created under it.)
# mount –t acfs /dev/asm/vol1-181
/u01/app/grid/acfsmounts/data_vol1
[oracle@linux12c ~]$ mount | grep acfs
/dev/asm/vol1-181 on /u01/app/grid/acfsmounts/data_vol1
type acfs (rw)
# Optionally, do a test storage snapshot creation
directly from the OS:
Storage
snapshots are created using the acfsutil snap command. Each snapshot must have
a name – it should be a valid os folder name.
Below, we specify the date
of creation as the snapshot name (10mar2014).
[grid@linux12c bin]$ /sbin/acfsutil snap create -r
10mar2014 /u01/app/grid/acfsmounts/data_vol1
acfsutil snap create: Snapshot operation is complete.
# Viewing file system info using acfsutil from the
os.
We can see the file system
details with 1 snapshot being listed.
$ /sbin/acfsutil info fs
/u01/app/grid/acfsmounts/data_vol1
ACFS Version:
12.1.0.1.0
flags: MountPoint,Available
mount time: Mon Mar 10 13:18:06 2014
volumes: 1
total size: 6442450944
total free:
1989275648
primary volume:
/dev/asm/vol1-181
label:
flags: Primary,Available,ADVM
on-disk
version: 39.0
allocation
unit: 4096
major,
minor: 252, 92673
size: 6442450944
free: 1989275648
ADVM
diskgroup DATA
ADVM resize
increment: 33554432
ADVM
redundancy: unprotected
ADVM stripe
columns: 4
ADVM stripe
width: 131072
number of
snapshots: 1
snapshot space
usage: 285282304
replication
status: DISABLED
This completes the environment set up stage.
Stage # 3 – Creation of a test database on the file system
Create the
CDB using DBCA, specifying the acfs mount point as the storage location.
Below we
list the databases and datafiles contained within the new PDB. Note that all
the datafile are stored under the file system exposed by ACFS.
SQL> select name from v$pdbs;
NAME
------------------------------
PDB$SEED
TOOLS
SQL > select con_id, FILE_NAME from cdb_data_files
order by con_id;
CON_ID FILE_NAME
----------
--------------------------------------------------------------------------------
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/system01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/sysaux01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/undotbs01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/users01.dbf
2
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/pdbseed/system01.dbf
2
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/pdbseed/sysaux01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/SAMPLE_SCHEMA_users01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/sysaux01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/example01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/system01.dbf
10 rows selected.
Stage
# 4 – PDB duplication using the storage snapshot feature.
# Ensure that the source database – TOOLS is in
read-only mode before clone.
This is required
for creating a PDB from an existing PDB, when we use the CREATE PLUGGABLE
DATABASE…FROM statement.
SQL> alter pluggable database tools close;
Pluggable database altered.
SQL> alter pluggable database tools open read only;
Pluggable database altered.
# Create the snapshot based clone (note the SNAPSHOT
COPY syntax below):
The CREATE
TABLE DDL is shown below. The command requests a copy of the TOOLS to be
created in the same database, with a new name TOOLSCOPY. The SNAPSHOT COPY
specifies that the duplication should be done using storage snapshots. The
storage snapshot function is provided by the underlying ACFS drivers.
create pluggable database TOOLSCOPY from TOOLS
file_name_convert=('/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS',
'/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLSCOPY') SNAPSHOT COPY
/
SQL> @create_snap.sql;
Pluggable database created.
# Open the new db in read-write mode at least once
to integrate it with the CDB.
SQL> alter pluggable database toolscopy open read
write;
Check the
status of the cloned database to make sure its integrated properly into the CDB.
SQL> select pdb_name,status from cdb_pdbs;
PDB_NAME
STATUS
-------------------- -------------
TOOLS
NORMAL
PDB$SEED
NORMAL
TOOLSCOPY
NORMAL
# Connect to
the newly clone database and create a table to test it.
To test
the newly cloned database, we connect to it using the HR user which it
inherited from the source. We will
create a copy of that table to make sure that we are able to modify the
database.
[oracle@linux12c ~]$ sqlplus hr/hr@localhost:1521/TOOLSCOPY
SQL*Plus: Release 12.1.0.1.0 Production on Mon Mar 10
15:15:28 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Last Successful login time: Mon Mar 10 2014 15:15:18
+08:00
Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0
- 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real
Application Testing options
SQL> create table
test as select * from employees;
Table created.
SQL> select sys_context('USERENV','CON_NAME') from
dual;
SYS_CONTEXT('USERENV','CON_NAME')
--------------------------------------------------------------------------------
TOOLSCOPY
SQL> exit
# View the data files within the CDB after duplication
Below, we
query the database datafiles and the red ones are the ones being supported by
the storage snapshot.
SQL> select con_id, file_name from cdb_data_files order
by 1;
CON_ID FILE_NAME
------
------------------------------------------------------------------------------------------
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/system01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/sysaux01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/undotbs01.dbf
1
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/users01.dbf
2
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/pdbseed/system01.dbf
2
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/pdbseed/sysaux01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/SAMPLE_SCHEMA_users01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/example01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/sysaux01.dbf
3
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLS/system01.dbf
4
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLSCOPY/system01.dbf
4
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLSCOPY/example01.dbf
4
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLSCOPY/SAMPLE_SCHEMA_users01.dbf
4
/u01/app/grid/acfsmounts/data_vol1/oradata/CDB2/TOOLSCOPY/sysaux01.dbf
14 rows selected.
# View ACFS snapshot
information
From the
OS, issue the acfsutil snap into command, to display the snapshots. The command
expects the mount point as its argument.
Below we
can see the new storage snapshot created as a result of the create pluggable
database command.
When the
TOOLSCOPY database is updated, the read-write snapshot is automatically updated
by ACFS. The possible use of this feature is rapid creation of an independent
copy of the source database.
oracle@linux12c ~]$ /sbin/acfsutil snap info
/u01/app/grid/acfsmounts/data_vol1
snapshot
name:
F43B485145091279E0430100007F293D
RO snapshot
or RW snapshot: RW
parent
name:
/u01/app/grid/acfsmounts/data_vol1
snapshot
creation time: Mon Mar 10 13:58:37
2014
snapshot name: 10mar2014
RO snapshot or RW snapshot: RO
parent name:
/u01/app/grid/acfsmounts/data_vol1
snapshot creation time: Mon Mar 10 13:20:26 2014
number of
snapshots: 2
snapshot space
usage: 979169280
This
concludes the exercise.
