Top 100+ Automatic Storage Management (asm) Interview Questions And Answers
Question 1. What Is Asm?
In Oracle Database 10g/11g there are forms of times: database and ASM instances. The ASM instance, which is commonly named +ASM, is started with the INSTANCE_TYPE=ASM init.Ora parameter. This parameter, whilst set, indicators the Oracle initialization recurring to begin an ASM example and now not a popular database example. Unlike the usual database example, the ASM instance carries no bodily documents; which includes logfiles, controlfiles or datafiles, and simplest requires some init.Ora parameters for startup.
Upon startup, an ASM instance will spawn all the basic background methods, plus some new ones which are precise to the operation of ASM. The STARTUP clauses for ASM times are similar to the ones for database instances. For example, RESTRICT prevents database times from connecting to this ASM example. NOMOUNT starts offevolved up an ASM example with out mounting any disk organization. MOUNT option simply mounts all described diskgroups For RAC configurations, the ASM SID is +ASMx example, wherein x represents the example number.
Question 2. What Are The Key Benefits Of Asm?
ASM affords filesystem and volume manager capabilities built into the Oracle database kernel. Withthis capability, ASM simplifies garage management duties, such as developing/laying out databases and disk space management. Since ASM lets in disk control to be completed the usage of acquainted create/modify/drop SQL statements, DBAs do not need to study a brand new skill set or make vital decisions on provisioning.
The following are some key advantages of ASM:
ASM spreads I/O lightly across all available disk drives to prevent hot spots and maximize performance.
ASM eliminates the want for over provisioning and maximizes storage resource usage facilitating database consolidation.
Inherent huge document help.
Performs computerized on line redistribution after the incremental addition or elimination of garage ability.
Maintains redundant copies of records to provide high availability, or leverages third birthday party RAID capability.
Supports Oracle Database in addition to Oracle Real Application Clusters (RAC).
Capable of leveraging third celebration multipathing technologies.
For simplicity and less complicated migration to ASM, an Oracle database can comprise ASM and non-ASM files.
Any new documents may be created as ASM files even as present files can also be migrated to ASM.
RMAN instructions allow non-ASM controlled files to be relocated to an ASM disk group.
Enterprise Manager Database Control or Grid Control can be used to manage ASM disk and document activities.
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Question 3. Describe About Asm Architecture.?
Automatic Storage Management (ASM) instance. Instance that manages the diskgroup metadata
Logcal grouping of disks
Determines document mirroring options
LUNs provided to ASM
Files which can be saved in ASM disk corporations are known as ASM files, this consists of database documents
Many databases can connect as clients to single ASM times
ASM example call have to most effective be +ASM best
One diskgroup can serve many databases
Question four. How Does Database Connects To Asm Instance?
The database communicates with ASM instance the usage of the ASMB (umblicus procedure) manner. Once the database obtains the vital extents from volume map, all database IO going forward is processed through by the database procedures, bypassing ASM. Thus we are saying ASM is not honestly inside the IO direction.
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Question five. What Init.Ora Parameters Does A User Need To Configure For Asm Instances?
The default parameter settings work perfectly for ASM.
The only parameters wanted for 11g ASM:
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Question 6. How Does The Database Interact With The Asm Instance And How Do I Make Asm Go Faster?
ASM is not within the I/O direction so ASM does not hinder the database file access. Since the RDBMS example is performing raw I/O, the I/O is as speedy as viable.
Question 7. Do I Need To Define The Rdbms Filesystemio_options Parameter When I Use Asm?
No. The RDBMS does I/O immediately to the uncooked disk gadgets, the FILESYSTEMIO_OPTIONS parameter is best for filesystems.
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Question eight. Why Oracle Recommends Two Disk Groups?
Oracle recommends two disk corporations to provide a stability of manageability, utilization, and performance.
Question 9. We Have A sixteen Tb Database. I’m Curious About The Number Of Disk Groups We Should Use; E.G. 1 Large Disk Group, A Couple Of Disk Groups, Or Otherwise?
For VLDBs you will probably emerge as with distinct storage tiers; e.G with some of our big clients they have Tier1 (RAID10 FC), Tier2 (RAID5 FC), Tier3 (SATA), and many others. Each such a is mapped to a diskgroup.
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Question 10. We Have A New App And Don’t Know Our Access Pattern, But Assuming Mostly Sequential Access, What Size Would Be A Good Au Fit?
For 11g ASM/RDBMS it's far recommended to use 4MB ASM AU for disk organizations. See Metalink Note 810484.1
Question eleven. Would It Be Better To Use Bigfile Tablespaces, Or Standard Tablespaces For Asm?
The use of Bigfile tablespaces has no bearing on ASM (or vice versa). In reality most database object associated selections are transparent to ASM.
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Question 12. What Is The Best Lun Size For Asm?
There is not any pleasant size! In most instances the garage group will dictate to you primarily based on their standardized LUN size. The ASM administrator merely has to communicate.
The ASM Best Practices and alertness characteristics to garage oldsters :
Need similarly sized / overall performance LUNs
Minimum of 4 LUNs
The ability requirement
The workload characteristic (random r/w, sequential r/w) & any reaction time SLA
Using this information , and their standards, the storage parents should construct a pleasant LUN institution set for you.
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Question thirteen. In 11g Rac We Want To Separate Asm Admins From Dbas And Create Different Users And Groups. How Do We Set This Up?
Separate Oracle Home for ASM and RDBMS.
RDBMS example connects to ASM the use of OSDBA institution of the ASM example.
Thus, software program proprietor for every RDBMS example connecting to ASM ought to bea member of ASM's OSDBA group.
Choose a unique OSDBA group for ASM instance (asmdba) than forRDBMS example (dba)
In 11g, ASM administrator needs to be member of a separate SYSASM organization toseparate ASM Admin and DBAs.
Question 14. Can My Rdbms And Asm Instances Run Different Versions?
Yes. ASM can be at a higher version or at decrease model than its patron databases. There’s two
-components of compatiblity
Diskgroup compatibility attributes:
Question 15. Where Do I Run My Database Listener From; I.E., Asm Home Or Db Home?
It is recommended to run the listener from the ASM HOME. This is particularly vital for RAC env, because the listener is a node-stage aid. In this config, you could create extra [user] listeners from the database homes as needed.
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Question sixteen. How Do I Backup My Asm Instance?
Not relevant! ASM has no files to backup, as its does no longer include controlfile,redo logs etc.
Question 17. When Should I Use Rman And When Should I Use Asmcmd Copy?
RMAN is the recommended and most whole and bendy method to backup and delivery database documents in ASM.
ASMCMD replica is right for copying unmarried files:
Supports all Oracle document kinds
• Can be used to instantiate a Data Guard environment
• Does not replace the controlfile
• Does not create OMF files
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Question 18. I’m Going To Do Add Disks To My Asm Diskgroup, How Long Will This Rebalance Take?
Rebalance time is closely pushed by way of the 3 gadgets
Amount of information presently within the diskgroup
IO bandwidth available on the server
ASM_POWER_LIMIT or Rebalance Power Level
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Question 19. We Are Migrating To A New Storage Array. How Do I Move My Asm Database From Storage A To Storage B?
Given that the brand new and antique garage are each visible to ASM, genuinely upload the new disks to the ASM disk organization and drop the antique disks. ASM rebalance will migrate records online.
Note 428681.1 covers the way to pass OCR/Voting disks to the new garage array
Question 20. Is It Possible To Unplug An Asm Disk Group From One Platform And Plug Into A Server On Another Platform (for Example, From Solaris To Linux)?
No. Cross-platform disk organization migration no longer supported. To move datafiles among endian-ness structures, you want to use XTTS, Datapump or Streams.
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Question 21. How Does Asm Work With Multipathing Software?
It works excellent! Multipathing software program is at a layer lower than ASM, and as a result is transparent.
You may also need to modify ASM_DISKSTRING to specify most effective the direction to the multipathing pseudo devices.
Question 22. Is Asm Constantly Rebalancing To Manage “warm Spots”?
No, ASM provides even distribution of extents throughout all disks in a disk group. Since each disk will equal variety of extents, no unmarried disk can be hotter than some other. Thus the solution NO, ASM does now not dynamically pass warm spots, due to the fact hot spots truely do no longer occur in ASM configurations. Rebalance only takes place on garage configuration modifications (e.G. Add, drop, or resize disks).
Question 23. What Are The File Types That Asm Support And Keep In Disk Groups?
Data Pump sell off sets
Data Guard configuration
Temporary information documents:
RMAN backup sets
Change monitoring bitmaps
Online redo logs:
RMAN statistics document copies
Transport records files
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Question 24. List Key Benefits Of Asm?
Stripes files instead of logical volumes
Provides redundancy on a file basis
Enables on line disk reconfiguration and dynamic rebalancing
Reduces the time significantly to resynchronize a transient failure through tracking adjustments at the same time as disk is offline
Provides adjustable rebalancing speed
Supports studying from reflected copy instead of number one replica for prolonged clusters
Is robotically set up as a part of the Grid Infrastructure
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Question 25. What Is Asm Striping?
ASM can use variable length information extents to help large documents, reduce reminiscence necessities, and enhance performance.
Each facts volume is living on an person disk.
Data extents encompass one or more allocation devices.
The statistics volume size is:
Equal to AU for the first 20,000 extents (zero–19999)
Equal to four × AU for the subsequent 20,000 extents (20000–39999)
Equal to 16 × AU for extents above forty,000
ASM stripes files the usage of extents with a rough technique for load balancing or a first-class method to lessen latency.
Coarse-grained striping is continually equal to the powerful AU length.
Fine-grained striping is constantly identical to 128 KB.
Question 26. How Many Asm Disk Groups Can Be Created Under One Asm Instance?
ASM imposed the subsequent limits:
63 disk groups in a storage device
10,000 ASM disks in a garage system
Two-terabyte most garage for every ASM disk (non-Exadata)
Four-petabyte most garage for each ASM disk (Exadata)
forty-exabyte most storage for each storage system
1 million documents for every disk institution
ASM report size limits (database limit is 128 TB):
External redundancy maximum document length is one hundred forty PB.
Normal redundancy maximum report length is 42 PB.
High redundancy maximum file length is 15 PB.
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Question 27. What Is A Diskgroup?
A disk group consists of multiple disks and is the fundamental object that ASM manages. Each disk group includes the metadata this is required for the management of area within the disk group. The ASM instance manages the metadata about the files in a Disk Group within the same manner that a document device manages metadata approximately its files. However, the substantial majority of I/O operations do not bypass thru the ASM instance. In a moment we are able to observe how file I/O works with admire to the ASM instance.
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Question 28. Can My Disks In A Diskgroup Can Be Varied Size? For Example One Disk Is Of 100gb And Another Disk Is Of 50gb. If So How Does Asm Manage The Extents?
Yes, disk sizes may be varied, Oracle ASM will manage information efficiently and shrewd by using putting the extents proportional to the dimensions of the disk in the disk institution, larger diskgroups have more extents than lesser ones.