What is Fail group?
Failure Groups are used to specify placement of mirrored copies so that each copy is on a disk in different Failure Groups. The simultaneous failure of all disks in a Failure Group does not result in data loss.
What is normal redundancy in ASM?
ASM allows NORMAL redundancy, in which a diskgroup is composed of two failgroups, or HIGH redundancy, in which a diskgroup is composed of three failgroups.
What are failure groups in ASM?
Failure groups are used to store mirror copies of data. When Oracle ASM allocates an extent for a normal redundancy file, Oracle ASM allocates a primary copy and a secondary copy. Oracle ASM chooses the disk on which to store the secondary copy so that it is in a different failure group than the primary copy.
What is striping and mirroring in ASM?
Striping spreads each file extent evenly across all disks in the assigned disk group. ASM also provides automatic mirroring of ASM files and allows the mirroring level to be specified by group. This mirroring occurs at the extent level.
What is the least number of failure groups in a high redundancy disk group?
A high redundancy disk group must contain at least three failure groups.
What is high redundancy in ASM?
HIGH redundancy is the ASM redundancy level recommended to run on production systems as each primary file extent has 2 mirrored copies on different failgroups while with NORMAL redundancy each primary file extent has only one mirrored file extent in a different failgroup.
How do I change redundancy of ASM Diskgroup?
Create a pfile from spfile, and shutdown the asm instance:
- SQL> create pfile=’/tmp/init+ASM. ora’ from spfile;
- File created.
- SQL> shut immediate;
- ASM diskgroups dismounted.
- ASM instance shutdown.
What is data striping in Oracle?
ASM striping is the process of dividing a file into 1 MB extents and spreading the extents evenly across all disks in the disk group. An extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information.
What are the different types of Stripings in ASM & their differences?
Coarse-grained striping provides load balancing for disk groups while fine-grained striping reduces latency for certain file types by spreading the load more widely. To stripe data, Oracle ASM separates files into stripes and spreads data evenly across all of the disks in a disk group.
How do you change ASM Diskgroup redundancy from external to normal?
Moving the ASM spfile from External to Normal Redundancy
- Stop the CRS on all the nodes.
- Take a backup of existing spfile.
- Then Move the spfile to GRID_HOME/dbs folder.
- Create a directory structure in new diskgroup for ASMPARAMETER file.
- Now move the spfile from the filesystem location to new diskgroup.
How many disks are in ASM redundancy?
ASM includes the ability to mirror diskgroups to protect data from physical failures. Available protection levels are NORMAL (one mirror), HIGH (two mirrors) or EXTERNAL where the data protection is handled by ScaleIO….ASM redundancy.
| ASM redundancy | Copies of voting disk | Number of failure groups required |
|---|---|---|
| Normal | 3 | 2 |
| High | 5 | 3 |
How do I move a database from one group to another?
Answer: Moving data files from one ASM diskgroup to another diskgroup involves these steps:
- Step 1: Get the data file name: select. file_name. from.
- Step 2: Identify the target diskgroup to migrate to: select. name. from.
- Step 3: Take the old data file offline: alter database datafile. ‘+MYDB_OLDDATA/mysid/app_data.nnn’
What is a failure group in Oracle?
There are always failure groups even if they are not explicitly created. If you do not specify a failure group for a disk, then Oracle automatically creates a new failure group containing just that disk, except for disk groups containing disks on Oracle Exadata cells.
What happens if I don’t specify a failure group for disk?
If you do not specify a failure group for a disk, then Oracle automatically creates a new failure group containing just that disk, except for disk groups containing disks on Oracle Exadata cells. A normal redundancy disk group must contain at least two failure groups.
What is failure Failure Group in ASM?
Failure groups are used to store mirror copies of data. When Oracle ASM allocates an extent for a normal redundancy file, Oracle ASM allocates a primary copy and a secondary copy.
How many failure groups are recommended for Oracle Partner status table?
Oracle recommends a minimum of three failure groups for normal redundancy disk groups and five failure groups for high redundancy disk groups to maintain the necessary number of copies of the Partner Status Table (PST) and to ensure robustness with respect to storage hardware failures.