Cloud Edition: Oracle Exadata Interview Questions and Answers

What kind of subscription options exists for Oracle Database Exadata Cloud Service?
  • Non-metered Subscription 
  • Metered Subscription 

What mean by Non-metered Subscription?
A non-metered subscription is an agreement to purchase a specific number of service units over a specific term. Consequently, the charge for a non-metered subscription is not related to actual service usage. Non-metered subscriptions are also referred to as standard subscriptions.

What mean by Metered Subscription?
Metered Subscription — With a metered subscription, you are charged based on your service usage. 

Two varieties exist:  
  • Pre-Paid — With a pre-paid subscription you pay an up-front amount to establish an account that is consumed as you use a service. 
  • Pay As You Go — With a pay as you go subscription you do not pay an upfront amount and are billed periodically for your actual service usage. 

What type of exadata configurations offered for oracle exadata cloud service in Oracle premises?
  • Quarter Rack
  • Half Rack
  • Full Rack system configurations

What type of exadata configurations offered if customer has Exadata cloud at customer palce?
  • Quarter Rack
  • Half Rack
  • Full Rack system configurations
  • Eighth Rack

What is SPARSE disk group?
The SPARSE disk group is required to support Exadata Cloud Service snapshots.  Exadata snapshots enable space-efficient clones of Oracle databases that can be created and destroyed very quickly and easily. 

What is the use of database snapshots?
Snapshot clones are often used for development, testing, or other purposes that require a transient database. 

What are the options to reconfigure storage for ASM disk group in exadata cloud service?
Submit a Service Request to Oracle
Delete and then re-create the Exadata Cloud Service instance

What will be the storage allocation ratio if backup is not on exadata and SPARSE disk group is not required?
  • DATA disk group - 80% of storage space
  • RECO disk group - 20% of storage space
  • SPARSE disk group - 0% 

Which access is mandatory to create Oracle Exadata Database Cloud Service?
Before you can create a database deployment with Exadata Cloud Service, you must have access to an Exadata Cloud Service instance

Which service level option you need to select while creating Oracle Exadata Database Cloud Service?
When creating a database deployment on Oracle Database Exadata Cloud Service, we need to select Oracle Database Exadata Cloud Service as the service level option. 

Which version of Oracle Database supported for Oracle Exadata Database Cloud Service?
  • Oracle Database 11g Release 2 
  • Oracle Database 12c Release 1 
  • Oracle Database 12c Release 2

Which type of database setup we can choose while deploying the database on Oracle Exadata Database Cloud Service?
  • Database Clustering with RAC 
  • Database Clustering with RAC and Data Guard Standby

Which storage options are available to store automatic database backup?
It can be either Cloud storage  or Exadata storage.

Which role will be created to start working on Oracle Exadata Database Cloud Service?
DBaaS Database Administrator 

What is the workflow for using Oracle Exadata Database Cloud Service?
  • Add and manage users and role
  • Create an SSH key pair
  • Create a service instance
  • Create a database deployment
  • Enable network access
  • Load data into the database
  • Monitor database deployments
  • Monitor the service
  • Patch a database deployment
  • Back up a database deployment

What is the recommended method to stop, start or restart compute node?
Oracle recommends that you use the Oracle Database Cloud Service console to stop, start and restart the compute nodes, rather than using an operating system command.

What kind of scaling are supported for Exadata in cloud service?
Two kinds of scaling operations are supported for an Oracle Database Exadata Cloud Service instance: 
  • Scaling within an Exadata system enables you to modify compute node processing power within the confines of your existing Exadata system. 
  • Scaling across Exadata system configurations enables you to move to a different Exadata system configuration. For example, from a Quarter Rack to a Half Rack.

What is bursting in exadata scaling?
With bursting, you can quickly scale up beyond your subscription level to cater for workload peaks. 

You can also scale back to the subscription level at any time. CPU cores beyond your subscription level are charged separately using an hourly rate for the bursting period.

When one should go for scale exadata across exadata system?
  • Processing power that is beyond the capacity of the current system configuration. 
  • Storage capacity that is beyond the capacity of the current system configuration. 
  • A performance boost that can be delivered by increasing the number of available compute nodes. 
  • A performance boost that can be delivered by increasing the number of available Exadata Storage Servers. 

How we can load data into Oracle Exadata Cloud Instance?
You load data into an Oracle database on Oracle Database Exadata Cloud Service using the same tools you would use for an Oracle database on another system. However transmission speeds across the internet can be slower.
  • Using SQL*Loader to Load Data into the Database
  • Using Oracle Data Pump Import to Load Data into the Database 
  • Using Transportable Tablespaces to Load Data into the Database
  • Using Pluggable Databases (PDBs) to Load Data into the Database 
  • Using Oracle Public Cloud Data Transfer Services to Move Large Data Sets

Which utility used to take backup in Oracle Exadata Database Service?
bkup_api 

Which utility used to patch  Oracle Database and Oracle Grid Infrastructure software in Oracle Exadata Database Service?
exadbcpatchmulti 

What pre-requites we should check before applying patches?
  • Confirms that the patch is available for download. 
  • Confirms connectivity to the required compute nodes. 
  • Verifies that there is enough space to apply the patch. 
  • Runs the opatch prereq command to validate that the specific patch requirements are met.

Which system user available to access the operating system in Oracle Exadata Database Service?
  • OPC
  • ORACLE
  • ROOT - It can be accessible using OPC user using SUDO access
  • GRID

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Oracle DBA: Moving to the Cloud

It is important to note that just because you will be moving to the cloud, it is not to say that the DBA you have in-house will be abdicating his or her responsibilities. 

There are duties and tasks that will change once the shift to the cloud occurs, but your DBA will still have a very valuable role to play in your organization. 

One of those roles is to act as a liaison between your company and the remote DBA since he has more knowledge of the inner workings of your enterprise and can offer valuable information that will then be used in the provision of quality services to you. With a better understanding of your needs, you can expect a better service from your cloud vendor.


Here we have mentioned some of the important tasks or skills which required as Cloud DBA apart from traditional DBA skills.
  • Design & Specifications of Database i.e. CPU, Memory, Disk Space, Future Growth, High Availability & Disaster Recovery (Yes even in Cloud, you have to consider HA & DR).
  • Creating & Configuration of Oracle Database is very simple in Cloud with Click of a Button or with REST API & JSON but someone need to invoke these Scripts or Click (Cloud DBA will perform this task)
  • As an Oracle Cloud DBA, you need to learn new tools for Start/Stop i.e. DBaaSCLI (Database as a Service Command Line Interface) or Database Service Console
  • Still, you have to Patch but using new tools like DBaaSCLI with DBPATCHM or RACCLI
  • You still have to do the Back-up and Recovery using new tools and Oracle Storage Service (OSS).
  • You still will be learning about Migration to the Cloud (Lift & Shift) and this is where you can expect a lot of work to migrate existing on-premise databases to Cloud.
  • You still will be learning about Disaster Recovery (or Data Guard ) in Cloud and setting up Disaster Recovery (DR) on Cloud for Data Center Failover (Yes this is not available out of Box & You as Cloud DBA will have to set it up).
  • You still will be configuring RAC on Cloud or you will be deploying maximum availability Architecture. Check my Video Blog on Setting Up RAC Database in Oracle Cloud
  • You still will be configuring OEM CC 13c: Hybrid Cloud Management to Manage both On-Premise & Cloud Database or using Oracle Management Cloud (OMC)
  • Understanding of Exadata components and features
  • Exadata administration skill


Introducing Oracle Exadata X7...!!!

Oracle announced the next-generation Oracle Exadata X7 with significant hardware and software enhancements in overall performance, storage capacity, network bandwidth, and automation.

Oracle Exadata is an Engineered System designed to be the ideal platform for all database workloads.  It features scale-out, database optimized compute, InfiniBand networking, and smart storage for fastest performance and low costs. Specialized algorithms vastly accelerate all types of database processing including OLTP, Analytics, and Consolidation. Exadata’s full-stack automation and optimization of all components slashes the need for skilled human labor, enabling reduced costs and improved reliability.  


Exadata’s simplicity, scalability, and reliability make it the foundation for the recently announced Oracle Autonomous Database Cloud.

Today, Exadata powers 4 out of 5 of the world’s biggest banks, telecoms, and retailers.  Exadata can be deployed on-premises, in Oracle Cloud, or using Oracle’s unique Cloud at Customer. 

Oracle 18c and Its Impact on DBAs

Oracle Database 18c the next generation of the industry-leading database.

Oracle introduces the world's first autonomous database cloud. Oracle Autonomous Database Cloud eliminates complexity, human error, and manual management, helping to ensure higher reliability, security, and more operational efficiency at the lowest cost.


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Oracle Exadata Cloud Machine Features and Benefits

Oracle Exadata Cloud Machine delivers the full power of the Oracle Exadata Cloud Service that resides in Oracle's public cloud to customers who require or prefer their databases to be located on-premises.

For many years, Oracle Exadata has been the platform of choice for running mission critical Oracle databases at thousands of customers, and the Oracle Exadata Cloud Machine extends this value proposition to those customers who want cloud benefits but cannot or aren't yet ready to move to a public cloud.


The business model is just like a public cloud subscription; the hardware and software is the same; Oracle experts monitor and manage the infrastructure; and the same tools used in Oracle's public cloud are used to provision resources on the Cloud Machine.

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Managing OS Statistics On Oracle Database Server

Operating system performance issues commonly involve process management, memory management, scheduling and storage management. 


Many times we get into the performance issue if we don't follow the common Oracle best practice like system parameters, improper swap allocation, hard/soft limit, not configuring hugepages wherever it requires.

If you have tuned the Oracle database instance and still need to improve performance, tune the OS, network and storage part.


Well, here we have given some of the basic statistics management which can help to boost the performance in your environment.

CPU Statistics: 

  • Doesn't exceed 95% in total
  • Check DB share on CPU 

Virtual Memory Statistics: 

  • Validate that memory usage does not increase after the system has reached a steady state after startup

Disk I/O Statistics: 

  • Current response time should be between 5 to 20 ms for a single block IO the length of the disk queues shouldn't exceed two

Network Statistics: 

  • Look at the network round-trip ping time and the number of collisions
  • Investigate it, if the network is causing large delays in response time

Reducing Disk Contention: 

  • Increase the number of disks in the storage system 
  • Separate the database and the redo log files 
  • For a large table, use partitions to reduce I/O 
  • Stripe the data either manually or by using a RAID disk-striping system 
  • Invest in cutting-edge technology, such as file caching, to avoid I/O bottlenecks 
  • Consider using ASM 

Top 10 Facts About Oracle Exadata Cloud Machine

This post is about the top facts about Oracle Exadata Cloud Machine from technical and business perspective.

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1. On-premise licenses cannot be transferred to ExaCM.

2. The minimum commitment to both the ExaCM and OCM is 4 years and the minimum configuration is Eighth Rack.

3. The subscription price for Oracle Database Exadata Cloud Machine X6 Eighth Rack is $40,000 per month (= $2,500 X 16) and that includes all DB options/features, Exadata Software and OEM DB Packs.

4. Standalone products such as Oracle Secure Backup and Oracle GoldenGate are not included in the ExaCM subscription. 

Only the database options (such as RAC, In-Memory, Partitioning, Active Data Guard, etc.), the database OEM packs and the Exadata storage server software are included.

5. ExaCM requires Oracle Cloud Machine to deploy Exadata Cloud Control Plane (separate subscription). OCM subscription requires similar minimum term commitment as ExaCM. 

If a customer already has an OCM, that can be leveraged to deploy Exadata Control Plane at no extra cost. One OCM Model 288 can manage 6 ExaCM Full Racks (i.e. 24 ExaCM Quarter Racks or 12 ExaCM Half Racks). 

Theoretically one OCM can support a much larger number of ExaCM full racks: about 50.

6. The 1/8th rack SKU is very similar to the on-premises 1/8th rack – i.e. minimum configuration of 16 OCPUs (cores), 240 GB RAM per database server, 144 TB raw storage (42 TB usable), 19.2TB of Flash. 

Compared to the Quarter Rack, it ships with less RAM, disk storage and flash. Those will be field installed if the customer chooses to go for the 1/8th to Quarter Rack upgrade. 

Note that this 1/8th rack enables customers to have an entry level configuration that is similar to what exists in Exadata Cloud Service.

7. Hourly Online Compute Bursting is supported with ExaCM. The commercial terms are the same as in Exadata Cloud Service – i.e. 25% premium over the Metered rate, calculated on an hourly basis. 

Customers can scale up or down, dynamically. Bursting does not kick in automatically based on load. Bursting of OCPUs needs to be configured by customers as needed. 

Once customer initiates bursting, the OCPU update is done dynamically without downtime. Customers will be billed later on the hours of bursting usage. Price: $8.401 per OCPU per hour.

8. If Cloud Control Plane is down, it doesn’t affect the availability of steady state runtime operations. However, cloud-based management (e.g. selfservice UI and REST API access) will be impacted.

9. Access: the Exadata Cloud Machine compute nodes are each configured with a Virtual Machine (VM). You have root privilege for the Exadata compute node VMs, so you can load and run additional software on the Exadata compute nodes. 

However, you do not have administrative access to the Exadata infrastructure components, including the physical compute node hardware, network switches, power distribution units (PDUs), integrated lights-out management (ILOM) interfaces, or the Exadata Storage Servers, which are all administered by Oracle.

10. Patching and backups: you can produce a list of available patches using the exadbcpatchmulti command as follows

# /var/opt/oracle/exapatch/exadbcpatchmulti -list_patches 
-sshkey=/home/opc/.ssh/id_rsa 
-oh=hostname1:/u01/app/oracle/product/12.2.0.1/dbhome_1

When you create a database deployment on Exadata Cloud Machine, you must choose from the following automatic backup configuration options:

– Remote Storage Only: uses remote NFS storage to store periodic full (RMAN level 0) backups and daily incremental backups, with a seven day cycle between full backups and an overall retention period of thirty days.

– None: no automatic backups are configured. Automatic backups cannot be configured later if you select the None option when you create a database deployment.

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Top Two Parameters in Oracle Exadata

You must have question in your mind that why only two parameters as there are n number of parameters related Exadata and all have it's own importance.

Well, we have choose these two because exadata performance more over dependent on these parameters and major two functionality works on these parameters.

These two parameters are:

_KCFIS_STORAGEIDX_DISABLED
CELL_OFFLOAD_PROCESSING


_KCFIS_STORAGEIDX_DISABLED

- There is not much you can do to control storage index behavior. However, the developers have built in a few hidden parameters that provide some flexibility.

- Above parameter is one of them to control the storage index functionality on exadata.

- This is undocumented and hidden parameter which is used to control the storage index function. It is highly recommended to check with the Oracle support before using it. 

- This parameter tells oracle storage if storage index need to be used while performing query execution. 

- It is used to enable and disable the usage of storage index when exadata is used for the database. 

- By default it is FLASE means storage index is enabled. If you need to disable the usage of storage index than make the value of this parameter TRUE.

Disable storage index:

SQL>alter system set _KCFIS_STORAGEIDX_DISABLED=TRUE;

Enable storage index:

SQL>alter system set _KCFIS_STORAGEIDX_DISABLED=FALSE;

You can also test this on session level.


CELL_OFFLOAD_PROCESSING

- Second parameter is related to the smart scan function of exadata. There are several parameters that apply to offloading. 

- The main one is CELL_OFFLOAD_PROCESSING, which turns offloading on and off.

- By default the value of this parameter is TRUE which means smart scan is enabled. In case if you want to test measure the performance of database using or without smart scan , you can use this parameter. 

- If it is disabled, it means that predicate filtering and storage indexes cannot be used to cut down the volume of data.

Disable smartscan:

SQL>alter system set CELL_OFFLOAD_PROCESSING=FALSE;

Enable smartscan:

SQL>alter system set CELL_OFFLOAD_PROCESSING=TRUE;

This parameter also can be tested on session level.

Why Exadata for Oracle Databases?

Many time it comes in our mind that why we should go for Exadata, what benefits we can get if we go for Exadata so here we have given some views based on the Exadata architecture, experience and features. This is the most common question in interview.



No doubt there can be many more advantages than what we have given below as we have only given high level views.

  • Exadata is high performance and high available pre-configured device.
  • It consists of servers,storage networking and software in single pre-configured box which is massively scalable, secure and redundant.
  • Multiple compression tiers are available on Exadata which can help customer to compress data as per business requirement to save storage space.
  • Implementation time is very less compare to non-Exadata systems as it's comes as pre-configured and pre-tested.
  • In case on any issue with the Exadata than we need to communicate with only single vendor which doesn't required to contact multiple vendor like non-Exadata setup so solution of issue could be done quicker.
  • Only DMA (Database Machine Administrator) would be required to manage the Exadata so it can manage with lower TCO which reduce the huge cost of manageability.
  • Exadata provides extreme performance for both DW and OLTP databases which is making it and ideal platform for database consolidation.

Top 14 Commands for Exadata Health Check

There are multiple ways, utilities or commands to monitor Exadata machine. Here we have mentioned the list of dcli commands which can help to get the list of cell alerts, resource consumption details and configuration details in shortest time.


Exadata alert

dcli -l root -g ~/cell_group "cellcli -e list metriccurrent where alertState!=\'Normal\'"

Exadata cell CPU utilization

dcli -l root -g ~/cell_group "cellcli -e list metriccurrent CL_CPUT"

Exadata cells flashdisk with status NOT present

dcli -l root -g ~/cell_group "cellcli -e list physicaldisk attributes name, id, slotnumber where disktype=\"flashdisk\" and status=\'not present\'"

Exadata cell current temperature

dcli -l root -g ~/cell_group 'cellcli -e list cell detail' | egrep temperature 

Exadata alert history

dcli -l root -g ~/cell_group "cellcli -e list metrichistory where alertState!=\'Normal\'" 

Exadata cells battery replacement checks

dcli -l root -g ~/cell_group '/opt/MegaRAID/MegaCli/MegaCli64 -adpbbucmd -aALL' |grep replaced

Exadata cells harddisk with status NOT present

dcli -l root -g ~/cell_group "cellcli -e list physicaldisk attributes name, id, slotnumber where disktype=\"harddisk\" and status=\'not present\'" 

Exadata cells services checks

dcli -l root -g ~/cell_group 'cellcli -e list cell detail' | egrep '(cellsrvStatus)|(msStatus)|(rsStatus)'

Exadata cells memory checks

dcli -l root -g ~/cell_group --vmstat="-a 3 2"

Exadata physical memory checks

dcli -g ~/all_group -l root "cat /proc/meminfo | egrep '^MemTotal:|^MemFree:|^Cached:

Exadata physical disk checks

dcli -g ~/all_group -l root /opt/MegaRAID/MegaCli/MegaCli64 AdpAllInfo -aALL | grep "Device Present" -A 8

Exadata cell fan status

dcli -l root -g ~/cell_group 'cellcli -e list cell detail' | egrep fan 

Exadata storage cell model detail

dcli -l root -g ~/cell_group 'cellcli -e list cell detail' | egrep makeModel -- For cell

dcli -l root -g ~/dbs_group 'dmidecode -s system-product-name'  -- For DB node

Exadata cells power status

dcli -l root -g ~/cell_group 'cellcli -e list cell detail' | egrep power


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Top 7 Database Views To Monitor Exadata

There are multiple ways to monitor the Exadata. Below 7 views will help to monitor Exadata in terms of history and current statistic of Exadata.


V$CELL—provides information about cell IP addresses mentioned in the cellip.ora file


CELL_PATH - IP addresses of the cell.
CELL_HASHVAL - A numeric hash value for the cell.

V$CELL_STATE—provides information about all the cells accessible from the database client


CELL_NAME - IP addresses of the cell.
STATISTICS_TYPE - statistics type, such as thread_stats.
OBJECT_NAME - key for a specific statistics type, such as the thread ID if STATISTICS_TYPE is thread_stats.
STATISTICS_VALUE - statistic values in an XML document with attribute and value pairs.


V$CELL_THREAD_HISTORY—contains samples of threads in the cell collected by the cell server


CELL_NAME - IP addresses of the cell.
SNAPSHOT_ID - ID of the snapshot(NUMBER).
SNAPSHOT_TIME - date and time of the snapshot.
THREAD_ID - thread ID (NUMBER).
JOB_TYPE - job that the thread was running when the snapshot was taken.
WAIT_STATE - A unique state that identifies the location of the wait, if any exists.
WAIT_OBJECT_NAME - Object being waited on, if any exists. For example, the mutex name.
SQL_ID - The identifier of the SQL command that the client was processing for the job that is running.
DATABASE_ID - ID of the database (NUMBER).
INSTANCE_ID - ID of the instance (NUMBER).
SESSION_ID - ID of the session (NUMBER).
SESSION_SERIAL_NUM - session serial number (NUMBER).


V$CELL_REQUEST_TOTALS—contains historical samples of requests run by the cell


CELL_NAME - IP addresses of the cell.
SNAPSHOT_ID -ID of the snapshot(NUMBER).
SNAPSHOT_TIME - date and time of the snapshot.
STATISTICS_NAME - name of the statistic.
STATISTICS_VALUE - value of the statistic.

V$SYSSTAT - This is view what we often use for monitoring database and be able to use monitoring Exadata also.

V$SQL family of views contain columns that define the volume of data that may be saved by offloading (IO_CELL_OFFLOAD_ELIGIBLE_BYTES) and the volume of data that was actually returned by the storage servers (IO_INTERCONNECT_BYTES, IO_CELL_OFFLOAD_RETURNED_BYTES).

V$CELL_OFL_THREAD_HISTORY 


This interesting view records a ten-minute history of what cellsrv threads were doing, conceptually something like ASH for storage cells.