ASM files are stored in a disk group in the form of group of extents. In Oracle 10g extents are read from primary failgroup, if it is not available only then extents are read from secondary failgroup.
In Oracle 11g a node can be configured to read to a specific failgroup. This is useful in an Oracle RAC database where multiple nodes access same ASM instance. If one of the located remotely, ASM diskgroup is configured to be read.
QUESTION2 ASM Fast Mirror resynchronization takes place when-
1 the disk is online and ASM Mirror extent is updated
2 the disk is offline and ASM Mirror extent is updated
3 the disk is online and ASM Mirror segment is updated
4 the disk is offline and ASM Mirror segment is updated
ANS 2 the disk goes offline and due to a transient failure
EXPLANATION
ASM synchronizes the only updated extent. When a disk is offline for any reason momentarily, that is the transient failure time of the disk. ASM tracks the extents which were changed during this failure. When transient period repaired and disk is available back, ASM immediately resynchronizes ASM mirror extent which was updated during temporarily failure. The DISK_REPAIR_TIME defines a time slot during which the transient failure can be repaired and mirror disk is online back.
QUESTION3 Which of following SQL statement is true considering below example?
SQL>ALTER DISKGROUP dgrp1 SET ATTRIBUTE 'DISK_REPAIR_TIME = 22H';
1 The DISK_REPAIR_TIME can not exceed the 3.6 hours
2 During transient failure in the specified, extent will be written
3 The statement will raise an error since DISK_REPAIR_TIME has been assigned an invalid value
4 All of these
ANSWER 2 During transient failure in the specified, extent will be written
EXPLANATION
When the disk is repaired after the resynchronization process, extents are updated which were not written during transient failure. The DISK_REPAIR_TIME default is 3.6 hours. DISK_REPAIR_TIME is a time slot during which disk is repaired from the mirror disk. After repair the disk run the SQL statement
SQL> ALTER DISKGROUP DISK ONLINE
QUESTION4 In Oracle 11g, ASM has introduces two new compatibility attributes. These attributes purpose is-
1 disk group compatibility settings decides that current environment can use the latest ASM features
2 If disk group created with Oracle 11g be available for Oracle 1og client
3 A disk group compatible attribute settings can only be increased
4 All of these
ANSWER 4 All of these
EXPLANATION
Setting the compatibility feature for ASM disk group allows the use of disk group for oracle 10g and Oracle 11g databases. The disk group attributes COMPATIBLE.ASM and COMPATIBLE.RDBMS determine compatibility. The COMPATIBLE.RDBMS can always advances allowing ASM disk availability between Oracle versions. If it goes decrease, a new ASM disk has to be created. The COMPATIBLE.RDBMS and COMPATIBLE.ASM attribute can be set in conjunction with CREATE DISKGROUP statement.
QUESTION5 Which of the following is an ASM Mirroring feature?
1 ASM files are mirrored automatically within the tablespace maintained by Oracle
2 ASM files can be mirrored within a disk group
3 Maximum one copy of the ASM files is allowed to be mirrored
4 All of these
ANSWER 2 ASM files can be mirrored within a disk group
EXPLANATION
When mirroring for a file is specified, ASM automatically stores copies of the file extents in separate failure groups. The disk group can be specified as External redundancy, Normal redundancy and High redundancy. Only normal and high redundancy disk groups are applicable to Failure groups. By default all files are mirrored. By enabling two-way mirroring ASM keeps two copies of data extents. By enabling three-way mirroring ASM keeps three copies of data extents. The data extent holds the content of the file and made up of one or more allocation units.
QUESTION6 Which of the following describes the ASM Rolling Upgrade feature?
1 An ASM node can separately be upgraded in Oracle RAC environment
2 An appropriate version of Oracle Clusterware must exist on all nodes to use this feature
3 The ASM cluster should be in rolling forward mode.
4 All of these
ANSWER 4 All of these
EXPLANATION
The ASM Rolling Upgrade feature allows upgrading the ASM nodes separately. Before upgrading, the ASM cluster must be in Rolling Migration mode. This allows the instance to be operated in multi version environment. The correct version of software must be installed before performing the upgrade. Since the rolling upgrade can be performed on several nodes, each instance joins the cluster while migration taking place. Example
ALTER SYSTEM START ROLLING MIGRATION TO NUMBER;
ALTER SYSTEM START ROLLING MIGRATION;
QUESTION7 Which is true in context of Preferred Mirror Read?
1 An ASM instance can be forced to read a particular mirror copy
2 By default instance read from primary copies
3 ASM-PREFFERED_READ_FAILURE_GROUPS initialization parameter is set to specify failure group as Preferred read
4 All of these
ANSWER 4 All of these
EXPLANATION
The ASM instance on a node can be configured t read from a preferred mirror copy which is also known as preferred read failure group. This feature is useful in Oracle RAC cluster where nodes and failure group are in remote location from each other. In this case the Oracle RAC node can be configured to read locally storage mirror copies. A multiple failure group can be specified by the ASM-PREFFERED_READ_FAILURE_GROUPS initialization parameter along with Failure Group Name. Once specified, marked as preferred read disks.
QUESTION8 Which of the following is not an ASMCMD utility job?
1 It is used to manage ASM diskgroups.
2 It has been improved for node recovery which is due to crash
3 It allow to create or drop disk groups
4 It allow to display the disk group space utilization
ANSWER 3 Let create or drop disk groups
EXPLANATION
ASMCMD is a command line utility is used to display files, directory and used space within ASM disk groups, can perform the node recovery.
It can be run at command prompt. Wild card such as '%', '*' can be used with this utility in conjunctions with few Unix commands such as ls, find etc.
ASMCMD command can not be used to create or drop the disk group or disk in the disk group.
ASMCMD provides ability to recreate pre existing ASM disk group with the same disk paths, disk names, failure groups, attribute, templates and aliases directory structure.
QUESTION9 Which of the following file copy option is allowed while using ASMCMD utility?
1 From one ASM disk group to other ASM disk group on same server
2 From one ASM disk group to other ASM disk group on remote server
3 From ASM disk group to OS
4 from OS file system to ASM disk group
ANS 4 All of these
EXPLANATION
In oracle 11g the ASMCMD allows the file to be copied from OS to ASM Disk Group or ASM Disk Group to OS and all the combination above.
QUESTION10 Which of the following is not an ASM instance operation?
1 ASM doesn't have the System Global Area and background processes
2 Several database instances shares the single ASM instance on the node
3 ASM and database instances require shared access to the disks in a disk group.
4 ASM instance do not manage the metadata of the disk group
ANSWER 4 ASM instance do not manage the metadata of the disk group
EXPLANATION
ASM instance is an improvement over the file system as maintained in prior to Oracle 11g databases. An ASM instance is combination of background process and SGA which is not very large as compared to database SGA. An ASM instance mounts the Disk Group and makes ASM files available. ASM do not actually mount the database.
There might be several database instances for different databases. All database instances share the same ASM instance.
ASM instances manage the metadata of the disk group and present it to the database instances as files.
The disks in a disk group are shared by the ASM and database instances during the disk group access. The metadata is the amount of space, the disk groups data file (ie. data extents) location etc.
A data extent can holds the contents of a file and consists of one or more allocation units on a specific disk.
QUESTION11 One or more DISK makes the disk group where metadata stores. Which is not a DISK feature?
1 Disks are added to add more storage space to disk group
2 The FORCE option add a blank disk to disk group even if the disk already exists
3 A disk can belong to several disk groups
4 Disk name is automatically generated by the system but can be named explicitly
ANSWER 3 A disk can belong to several disk groups
EXPLANATION
One or multiple disks can be added to the disk group increase disk group storage space. When a disk is added to the disk group with FORCE option and if the disk already belongs to any disk group, data is deleted. A disk can be associated only with a particular disk group and can not be part of another disk group.
While adding or creating the disk to the disk group, the NAME clause let explicitly assign the names to the disks. If name clause is omitted, system generates names like diskgroupname_n, where n is any number.
QUESTION12 Rebalancing operation on the disk group means-
1 Tuning meta-data of disk group
2 Disk groups can be rebalanced using proper SQL command
3 Redistributing data among disk group
4 All of these
ANSWER 4 All of these
EXPLANANTION
ASM rebalances the disk group to evenly distribute the data. The REBALANCE POWER of the rebalance operation can be set from 0 to 11. If this value set to zero, stop the rebalancing from taking place. If the POWER REBALANCE POWER is ignored, the ASM_POWER_LIMIT parameter value is used
A DBA can decide rebalancing as per database need. There might be a situation to add or delete the disk from disk group. So it is good to choose the rebalancing at this point of time when you have added and deleted disks. Disk groups are rebalanced manually using the REBALANCE clause with ALTER DISKGROUP statement.
QUESTION 13 Which is not a valid privilege for authentication to connect An Oracle ASM instance?
1 SYSDBA
2 SYSOPER
3 SYSASM
4 SYSTEM
ANSWER 4 SYSTEM
EXPLANATION
An Oracle ASM instance can be accessed by using system privileges, SYSASM, SYSDBA, or SYSOPER. SYSASM privilege is new in Oracle 11g to perform ASM administrative tasks. The operating system groups can be assigned the privileges on Oracle ASM. Then all users are authenticated as the operating system authentication groups. These are valid Operating System Groups and can be assigned for all of these privileges-
OSASM group- Granted SYSDABA privileges Oracle ASM instance and provide full administrative rights
OSDBA group - Granted the SYSDBA privilege and allows access to Oracle ASM data
OSOPER group- Granted the SYSOPER privilege and provides operations such as startup, shutdown, mount, dismount, and check disk group
QUESTION14 Which is not a valid operation to manage the data in disk groups?
1 Data in disks in the disk group is allocated in terms of Extents
2 The ASM disk in a disk group is divided into Allocation Units.
3 Initially ASM data store in shared pool and accessed by disk groups.
4 More disks can be added by specifying AU size for more storage
ANSWER 3 Initially ASM data store in shared pool and accessed by disk groups.
EXPLANATION
Prior to Oracle 11g, disk groups required memory from the shared pool for every extent. Minimum unit for storage is an extent not a block. An allocation unit is the minimum segment of the disk in a disk group which is assigned to a file. So if database size is larger, it requires a lot of memory in the shared pool to store extents.
In Oracle Database 11g, the extent size needs not to be equal to the AU sizes. The extent size is 1MB when the file is created and can be increased from1 to 64MB when the file reaches a certain limit. An appropriate extent size is automatically allocated by the ASM instance.
CREATE DISKGROUP dskgroup1
EXTERNAL REDUNDANCY
DISK '/dir1/dir2/dsk1'
ATTRIBUTE 'au_size'='20M';
QUESTION15 In which of the following conditions the RESTRICTED mode can be used to mount a disk group?
1 to perform rebalancing operation in Oracle RAC
2 to disallow users to access disk groups among nodes
3 to add a disk in disk group to make it available in Oracle RAC
4 All of these
ANSWER 3 to add a disk in disk group to make it available in Oracle RAC
EXPLANATION
Each time when a disk is added or mounted to a disk group in Oracle RAC environment, ASM immediately start rebalancing process. Rebalancing process take to place to distribute the data among disks.
In this case, in prior oracle versions, the ASM interacted with the RDBMS instance using the lock mechanism to indicate changes in the block.
But this process does not work in the Oracle RAC since locks are managed within the database and there are several nodes as well. In oracle 11g a newly added diskgroup can be mounted with RESTRICT clause to make process faster and data is accessible once mounted.
SQL> alter diskgroup dg7 mount restricted;
QUESTION16 Which is not a required parameter for Oracle 11g ASM?
1 ASM_DISKSTRING
2 ASM_DISKGROUPS
3 INSTANCE_TYPE
4 INSTANCE_NAME
ANSWER 4 INSTANCE_NAME
EXPLANATION
ASM_DISKSTRING -The ASM_DISKSTRING initialization parameter is defined with the list of strings which limits the number of disks searches by ASM instance.
ASM_DISKGROUPS -ASM_DISKGROUPS lists the names of disk groups to be mounted. These disk groups are mounted by an Automatic Storage Management instance during instance startup or when use an ALTER DISKGROUP ALL MOUNT statement. This parameter is automatically updated when a disk group is added or mounted, dropped or dismounted.
INSTANCE_TYPE -INSTANCE_TYPE identifies whether the instance is a database instance or an Automatic Storage Management instance.
QUESTION 17 Which of the following is the minimum unit to hold ASM data?
1 Block
2 Extent
3 Segment
4 Allocation Unit
ANSWER 2 Extent
EXPLANATION
In oracle 11g when a table or indexes are created the minimum storage of unit allocated is an extent not block. Extent is composed of multiple bocks. The extent size can vary automatically by the ASM when required. Similarly when a file is created on the ASM disk group, the smallest unit is extent, not AU .
QUESTION18 A disk group can be dropped-
1 only if it is mounted
2 without mounting if not being accessed
3 with FORCE option even being accessed
4 with FORCE option only if not being accessed
ANSWER 3 with FORCE option even being accessed
EXPLANATION
The disk group must be mounted to perform the tasks such as:
- When a disk group has to be dropped and recreated
- When the disks of a disk group to be added to other disk group
In Oracle 10g, if one of the disks is being missed in a disk group, it can not be mounted. In Oracle 11g, a drop command with a force option can be used to drop the disk group.
SQL>DROP DISKGROUP dgtest1 FORCE
SQL>DROP DISKGROUP dgtest2 FORCE INCLUDING CONTENTS;
QUESTION19 Which of the following is a valid statement about au_size parameter while working with Orcle 11g?
1 The au_size attribute can not be used in ASM init.ora file
2 The au_size attribute is used while creating the disk group
3 The au_size attribute is used to set the Allocation Unit
4 All of these
ANSWER 4 All of these
EXPLANATION
From Oracle 11g on, extent can be allocated in larger size while creating a disk group. They can be in multiples of 2 up to 64 MB. The allocation size was fixed to 1 MB in oracle 10g where each extent corresponded to AU. If disk group is not created with the ATTRIBUTE 'au_size', automatically is managed by the ASM instance.
SQL>CREATE DISKGROUP dg_data1
EXTERNAL REDUNDANCY
DISK 'ORCL:dsk1, ORCL:dsk2
ATTRIBUTE 'au_size' = '8M';
QUESTION20 The laskdsk command is used with ASMCMD command line utility. Which of the following describe the laskdsk task?
1 it lists information about disks in disk group
2 It lists information about failure group in clustered environment
3 It lists information Allocation Unit and Extent
4 All of these
ANSWER 1 it lists information about disks in disk group
EXPLANATION
There are several enhancements in the command line utility ASMSCMD. lskdsk is one of them which is used in conjunction with ASMSCMD. lskdsk can lists the disk related information such as locations of disks in disk group, disk repair related information etc. If lskdsk is enters with no parameter, list the path of disks.
ASMCMD>Lskdsk
When used with -t, shows the repair time related information when the disk went inaccessible
ASMCMD>lsdsk -t
To display disks of a specific diskgroup, can use the -d flag
ASMCMD> lsdsk -t -d dg1
lskdsk make the use of v$asm_disk and gv$asm_disk the performance view in a clustered environment. These view are used if the ASM instance is up.
QUESTION21 The ASM rolling upgrade provides higher level of availability in Oracle RAC environment. Which of the following is not a constraint before starting ASM rolling upgrade?
1 Each ASM instances must be on the same Oracle version
2 Each ASM instance must be in rolling upgrade mode
3 Each ASM instance must be shutdown
4 Each ASM instance must communicate with database instance
ANSWER 4 Each ASM instance must communicate with database instance
EXPLANATION
To perform rolling upgrade, each ASM instance must be in rolling upgrade mode in RAC environment. Instances might be placed in that mode using-
SQL>ALTER SYSTEM START ROLLING MIGRATION TO 11.2.0.2;
This command doesn't start the rolling migration just communicate with all ASM instances in a RAC. It informs other ASM instances of RAC that it is preparing to start an upgrade. Having enabled each ASM instance, the current status can be checked with the following statement.
SQL>select sys_context('sys_cluster_properties','cluster_state') from dual;
If instance is a part of rolling upgrade, this above statement displays the value "Rolling Migration" or "Normal"
It is necessary that each ASM instance must be put into rolling migration mode and shutdown before software upgrade. However certain operation continues to work such as mount or dismount disk group, ASM and database instance shutdown, startup etc.
Add or drop a disk to the disk group and rebalancing operation is not permitted during software upgrade.
QUESTION22 The parameter asm_preferred_read_failure_groups is used to read the disk groups of a failure group in multiple instance environment. Which of the following is not true while using this parameter?
1 even after specifying the disk groups, primary failure group is always read first
2 after specifying the disk groups, it becomes the preferred failure group and read first
3 Instances can access preferred failure group after they are set by this parameter
4 the parameter needs to be set at each instance with ALTER SYSTEM command
ANSWER 1 even after specifying the disk groups, primary failure group is always read first
EXPLANATION
This parameter can be used to specify preferred one or more failure group name separated by commas. Example
ALTER SYSTEM
SET ASM_PREFERRED_READ_FAILURE_GROUPS = 'dskG1.data1', 'dskG1.data2', 'dskG1.data3'';
Where dskG1 is disk group name and data1, data2… are the failure group name.
This parameter ASM_PREFERRED_READ_FAILURE_GROUPS is useful to let specify the disk group names to the failure group. In Oracle 10g the primary failure group is read. With Oracle 11 a failure group not necessarily read the primary failure group and enables to access disk groups being specified against a failure group using this parameter. Setting up disk group in this way one instance let access the failure group of other instance or other instance read from first instance. Once the disk groups are specified, they are the preferred group to be read for that instance.
QUESTION23 Which of the following command has been enhanced to be used with ASMCMD utility in Oracle 11g database?
1 lsdg
2 lsct
3 lskdsk
4 All of these
ANSWER 4 All of these
EXPLANATION
lsdg command lists all disk groups and their attributes using v$asm_diskgroup. Two new option are added to this disk group -c and -g. The option -g uses the GV$ASM_DISKGROUP view and can display relevant information. The option -c uses the view GV$ASM_DISKGROUP_STAT.
For lsct, the -g option has been added to the which reads the GV$ASM_CLIENT view
lskdsk is new command added to ASMCMD utility. It also read several V$ASM_ view and provide disks information of a disk group.
QUESTION24 Which of the following statement is true regarding renaming the ASM disk group?
1 When the disk group is going to be mounted on the same server, it should be renamed.
2 A configuration file must be generated which is read to rename the disk group by renamedg utility
3 The disk group should be dismounted before the renaming it.
4 All of these
ANSWER 4 All of these
EXPLANAION
An ASM disk group name must be renamed if is going to be mounted on the same server. The disk group should be dismounted before the renaming it. The disk group can be renamed by using a utility renamedg. The utility should be used in two steps. In the step it generated the configuration file. In second step it reads the configuration file and rename the disk.
QUESTION25 Which of the following is not a function of IDP (Intelligent Data Placement?
1 IDP enables specifying disk region on the ASM disks
2 IDP allocates a named space for ASM disks to be managed
3 IDP enables to add or exchange the space for ASM disks
4 All of these
ANSWER 1 IDP enables to specifying disk region on the ASM disks.
EXPLANATION
IDP to improve performance by specifying disk region. ASM IDP settings are specified in a file or in templates of the disk group. By using the disk region settings, it can be specified that frequently accessed data be stored on the outermost track known as hot region. Files being accessed in similar fashion located physically together and improve I/O performance.
