ASM Basics
- The smallest unit of storage written to disk is called an “allocation unit” (AU) and is usually 1MB (4MB recommended for Exadata)
- Very simply, ASM is organized around storing files
- Files are divided into pieces called “extents”
- Extent sizes are typically equal to 1 AU, except in 11.1 and 11.2 where it will use variable extent sizes that can be 1, 8, 64 AUs or 1, 4, 16 AUs respectively
- File extent locations are maintained by ASM using file extent maps.
- ASM maintains file metadata in headers on the disks rather than in a data dictionary
- The file extent maps are cached in the RDBMS shared pool; these are consulted when an RDBMS process does I/O
- ASM is very crash resilient since it uses instance / crash recovery similar to a normal RDBMS (similar to using undo and redo logging)
ASM Diskgroups
Creating Diskgroup:
CREATE DISKGROUP disk_group_1 NORMAL
REDUNDANCY
FAILGROUP failure_group_1 DISK
‘/devices/diska1’ NAME diska1,
‘/devices/diska2’ NAME diska2,
FAILGROUP failure_group_2 DISK
‘/devices/diskb1’ NAME diskb1,
‘/devices/diskb2’ NAME diskb2;
NOTE : The above disk group given as NORMAL redundancy, that means it contain 2 Fail groups (i.e., 2 sets of each data is maintained) also similarly for HIGH redundancy each data is made into thrice(1 original and 2 duplicates) so it makes 3 fail groups in Disk group
Drop disk groups
DROP DISKGROUP DATA INCLUDING CONTENTS;
Add disks
ALTER DISKGROUP DATA ADD DISK ‘/dev/sda3’;
Drop a disk
ALTER DISKGROUP DATA DROP DISK DATA_0001;
Resize all disks in a disk group
ALTER DISKGROUP DATA RESIZE ALL SIZE 100G;
UNDROP DISKS clause of the ALTER DISKGROUP
ALTER DISKGROUP DATA UNDROP DISKS;
Rebalance diskgroup
ALTER DISKGROUP DATA REBALANCE POWER 5;
Check Diskgroup
ALTER DISKGROUP DATA CHECK;
ALTER DISKGROUP DATA CHECK NOREPAIR;
Diskgroup Metadata Backup
md_backup -b asm_backup.mdb.txt -g data,fra
ASM Specific Init.ora Parameters
*.cluster_database=true
*.asm_diskstring=’/dev/sd*1′
*.instance_type=asm
*.shared_pool_size=100M
*.large_pool_size=80M
*.db_cache_size=60M
*.asm_diskgroups=’DATA’,’FRA’
Initialize ASM for non-RAC
./localconfig add
Manually start CSSD (non-RAC)
/etc/init.d/init.cssd start
Manually stop CSSD ( non-RAC)
/etc/init.d/init.cssd stop
Resetting CSS to new Oracle Home
localconfig reset /apps/oracle/product/11.1.0/ASM
ASM Dictionary Views
v$asm_alias —list all aliases in all currently mounted diskgroups
v$asm_client —list all the databases currently accessing the diskgroups
v$asm_disk —-lists all the disks discovered by the ASM instance.
v$asm_diskgroup —Lists all the diskgroups discovered by the ASM instance.
v$asm_file —Lists all files that belong to diskgroups mounted by the ASM instance.
v$asm_operation —Reports information about current active operations. Rebalance activity is reported in this view.
v$asm_template —Lists all the templates currently mounted by the ASM instance.
v$asm_diskgroup_stat —same as v$asm_diskgroup but does discover new disgroups. Use this view instead of v$asm_diskgroup.
v$asm_disk_stat —same as v$asm_disk but does not discover new disks. Use this view instead of v$asm_disk.
srvctl commands
ADD
srvctl add asm -n rac3 -i +ASM3 -o /opt/oracle/app/product/10.2.0/asm
ENABLE
srvctl enable asm -n rac3 -i +ASM3
DISABLE
srvctl disable asm -n rac3 -i +ASM3
START
srvctl start asm -n rac3
STOP
srvctl stop asm -n rac3
CONFIG
srvctl config asm -n rac1
REMOVE
srvctl remove asm -n rac1
STATUS
srvctl status asm
srvctl status asm -n rac1
MODIFY
srvctl modify asm -o -n rac1
ASMLIB commands ( as root)
/etc/init.d/oracleasm start
/etc/init.d/oracleasm stop
/etc/init.d/oracleasm restart
/etc/init.d/oracleasm configure
/etc/init.d/oracleasm status
/etc/init.d/oracleasm enable
/etc/init.d/oracleasm disable
/etc/init.d/oracleasm listdisks
/etc/init.d/oracleasm deletedisk
/etc/init.d/oracleasm scandisks
/etc/init.d/oracleasm querydisk /dev/sdb1
/etc/init.d/oracleasm createdisk /dev/sdb1 VOL1
/etc/init.d/oracleasm renamedisk /dev/sdb1 VOL1
asmcmd Commands
cd —–changes the current directory to the specified directory
du —–Displays the total disk space occupied by ASM files in the specified
ASM directory and all its subdirectories, recursively.
find —–Lists the paths of all occurrences of the specified name ( with wildcards) under the specified directory.
ls +data/testdb —-Lists the contents of an ASM director, the attributes of the specified file, or the names and attributes of all disk groups.
lsct —–Lists information about current ASM clients.
lsdg —-Lists all disk groups and their attributes
mkalias —-Creates an alias for a system generated filename.
mkdir —–Creates ASM directories.
pwd ——–Displays the path of the current ASM directory.
rm ——-Deletes the specified ASM Files or directories.
rm -f
rmalias ———Deletes the specified alias, retaining the file that the alias points to
lsdsk ———-Lists disks visible to ASM.
md_backup ——Creates a backup of all of the mounted disk groups.
md_restore ——Restores disk groups from a backup.
remap —-repairs a range of physical blocks on a disk.
cp ——copies files into and out of ASM.
SYSASM Role (Starting in Oracle Database 11g)
SQL> Grant sysasm to sys; —sysdba deprecated sqlplus / as sysasm
ASM Rolling Upgrades START
alter system start rolling migration to 11.2.0.2;
DISABLE
alter system stop rolling migration;
Database INIT parameters for ASM.
*.control_files=’+DATA/orcl/controlfile/control1.ctl’,’+FRA/orcl/controlfile/control2.ctl’
*.db_create_file_dest=’+DATA’
*.db_create_online_log_dest_1=’+DATA’
*.db_recovery_file_dest=’+DATA’
*.log_archive_dest_1=’LOCATION=+DATA’
*.log_file_name_convert=’+DATA/VISKDR’,’+DATA/VISK’ ##added for DG
Removing disks from an ASM disk group
SQL> select group_number,name from v$asm_disk order by group_number,name;
GROUP_NUMBER NAME
———— ——————————
1 ASM_ORADATA31_0000
1 ASM_ORADATA31_0001
1 ASM_ORADATA31_0002
1 ASM_ORADATA31_0003
1 ASM_ORADATA31_0004
1 ASM_ORADATA31_0005
2 ASM_ORADATA32_0000
2 ASM_ORADATA32_0001
2 ASM_ORADATA32_0002
2 ASM_ORADATA32_0003
2 ASM_ORADATA32_0004
2 ASM_ORADATA32_0005
12 rows selected.
SQL> ALTER DISKGROUP ASM_ORADATA31 DROP DISK ASM_ORADATA31_0005;
Diskgroup altered.
SQL> ALTER DISKGROUP ASM_ORADATA32 DROP DISK ASM_ORADATA32_0005;
Diskgroup altered.
SQL> select est_minutes from V$ASM_OPERATION;
EST_MINUTES
———–
6
MIGRATE to ASM using RMAN
run
{
backup as copy database format ‘+DATA’;
switch database to copy;
#For each logfile
sql “alter database rename ‘/data/oracle/VISK/redo1a.rdo’ to ‘+DATA’ “;
alter database open resetlogs;
#For each tempfile
sql “alter tablespace TEMP add tempfile” ;
}
Restore Database to ASM using SET NEWNAME
run
{
allocate channel d1 type disk;
#For each datafile
set newname for datafile 1 to ‘+DATA’;
restore database;
switch datafile all;
release channel d1;
}
Refer more : Master Note for Automatic Storage Management (ASM) (Doc ID 1187723.1)
Information Center: Install and Configure Oracle Automatic Storage Management (Doc ID 1522675.2)
