Interview_Questions_5 | Oracle ASM Architecture, Internals, Disk Groups & Redundancy

1. change diskgroup redundancy? 

TESTDB -> +DATA (External Redundancy)

Change redundancy of DATA diskgroup to NORMAL / HIGH? 

- Not possible 

2. change AU size of a diskgroup? 

TESTDB -> +DATA (AU=4MB)

Change AU size of DATA diskgroup to 1M/8MB?

- Not possible 

db_block_szie=8K 

AU=1MB/4MB 

-> bigger the AU/db_block_size better for OLAP/Datawarehouse database 

3. change diskgroup name? 

TESTDB -> +DATA groups

Change name of DATA diskgroup DATAC? 

- Possible (This need downtime for TESTDB)

DATA -> DATAC 

4. How to map asm disks to diskgroup?

/dev/oracleasm/disks/ASMDISK1 - OCR

/dev/oracleasm/disks/ASMDISK2 - DATA

/dev/oracleasm/disks/ASMDISK3 - RECO

select GROUP_NUMBER,NAME,FAILGROUP,PATH from V$ASM_DISK order by GROUP_NUMBER;

select GROUP_NUMBER,NAME from V$ASM_DISKGROUP order by GROUP_NUMBER;

ASMCMD [+] > lsdsk -G OCR

Path

/dev/oracleasm/disks/ASMDISK1

ASMCMD [+] > lsdsk -G DATA

Path

/dev/oracleasm/disks/ASMDISK2

ASMCMD [+] > lsdsk -G RECO

Path

/dev/oracleasm/disks/ASMDISK3

5. How to map asm disks to OS disks?

/dev/oracleasm/disks/ASMDISK1 - /dev/sdb1

/dev/oracleasm/disks/ASMDISK2 - /dev/sdc1

/dev/oracleasm/disks/ASMDISK3 - /dev/sdd1

oracleasm querydisk -d ASMDISK1

oracleasm querydisk -d ASMDISK2

oracleasm querydisk -d ASMDISK3

[root@oraclelab2 dev]# oracleasm querydisk -d ASMDISK1

Disk "ASMDISK1" is a valid ASM disk on device [8,17]

[root@oraclelab2 dev]# oracleasm querydisk -d ASMDISK2

Disk "ASMDISK2" is a valid ASM disk on device [8,33]

[root@oraclelab2 dev]# oracleasm querydisk -d ASMDISK3

Disk "ASMDISK3" is a valid ASM disk on device [8,49]

6. smallest unit of DB and smallest unit of ASM storage 

db_block_szie=8K 

AU=1MB/4MB 

-> bigger the AU/db_block_size better for OLAP/Datawarehouse database 

7. ASM Instance:

- instance only 

8. SPFILE (80+)

- SPFILE in diskgroup 

- create pfile from spfile 

9. ASM specific memory & ASM specific BG process 

10. connecting to DB, ASM, ASM storage 

11.  ASM storage structure / ASM logical structure  

AU, ASM Extents, ASM file, ASM disks, ASM diskgroup 

12. DB_BLOCK_SIZE Vs AU 

13. Redundancy (External, Normal, High) 

14. Why ASM? or advantages of ASM 

- Redundancy (External, Normal, High) 

- Fail Group 

- Striping 

- High speed read and write (Multiple parallel IO)

- Autorestart feature 

15. DB start-up sequence and ASM startup sequence 

16. ASM diskgroup administration 

create / alter / drop 

17. v$ Vs dba_ 

v$asm_diskgroup 

v$asm_disk

v$asm_operation

v$instance 

18. How to speed up this rebalance operation?

-> by using asm_power_limit parameter 

ASM_POWER_LIMIT - speed up rebalance 

19. How to estimate or get the rebalance time 

-> v$asm_operation

20. ASM, DB maintenance - Bounce

HAS (os process / os daemon) -> ASM -> DB 

crsctl check has

crsctl stop has

crsctl start has

srvctl status asm 

srvctl stop asm 

srvctl start asm 

srvctl status database -d TESTDB 

srvctl stop database -d TESTDB 

srvctl start database -d TESTDB 

21. diskgrup creation 

Creation DG - using command line 

Creation DG - using command GUI (./asmca) 

Regards,

Mallikarjun / Vismo Technologies

WhatsApp: +91 9880616848 / +91 9036478079

Cell: +91 9880616848 / +91 9036478079

Email: mallikarjun.ramadurg@gmail.com / vismotechnologies@gmail.com