Exadata Interview questions
what is eaxadata?
exadata ia pre configured engineered server from Oracle which is a combination of harware,storage,network bundles with OS and DB software
what is the exadata latest version?
the latest version of EXADATA is X8M released in Sep sep 2019
which version of exadata you have worked?
I have worked on X5,X6,X7,X8 , on OCI I have worked on X8M,X9
what are the major differeneces , you have seen in all these version?
X5 came with HCCC in 2015 and some ASM enhancements
X6 supported 12cR2
X7 came with larger memory configurations , faster storage and imporved MI for predictive analystics and also introduced ROE switches
X8 came with 100GIG infini band
X8M came with persistent memory
X9 came with 400GIG infiniband
On how many node RAC worked ?
I have worked on quarter node RAC and 1/8th RAC with 2 and 1 node cluster
How many VM you have created on 1/8th and quarter RAC?
I have created 3 VMS and 8 vms on quater node RACK
How do you created VM?
I have created VM using Oracle VM manager
I can create a VM using Vboxmanage command
Vboxmanage createVM --name myvm --ostype "oracle (64-bit)" --register
VBoxManage createhd --filename myvm.vdi --size 10240
VBoxManage storagectl myvm --name "SATA Controller" --add sata --controller IntelAhci
VBoxManage storageattach myvm --storagectl "SATA Controller" --port 0 --device 0 --type hdd --medium myvm.vdi
VBoxManage modifyvm myvm --memory 2048
VBoxManage modifyvm myvm --cpus 2
VBoxManage startvm myvm
what type of operarting system supported by Exadata?
windows,Linux,Oracle Linux,solaris,MACOS
what are the components of Exadata?
Exadata comprises of hardware, database server , storage server connected by high speed infini band network
DB Server
Cell Storage
InfiniBand Switch
Spine Switch
Cisco Switch
PDU
PDUs in Exadata systems are designed to provide redundancy and fault tolerance, meaning that if one PDU were to fail, the other PDUs in the rack would continue to provide power to the system without interruption. This helps ensure high availability and uptime for the Exadata system.
what is PEM
Persistent memory (PMEM) is a type of non-volatile memory technology that is used in Exadata systems to provide faster access to frequently accessed data.
In an Exadata system, PMEM is used to cache frequently accessed data from the database, such as indexes and hot tables. By storing this data in PMEM, the system can access it more quickly, which can improve query performance and reduce I/O bottlenecks.
what is a smart scan?
Smart Scan is a feature in Oracle Exadata that allows for faster data retrieval by offloading query processing to the storage servers. With Smart Scan, data is filtered, transformed, and processed closer to where it resides in the storage servers, reducing the amount of data that needs to be transferred over the network to the database servers.
what are the features of EXADATA?
Features of Exadata?
Smart Scan
Smart Flash Cache
IORM
Storage Index
EHCC (Exadata Hybrid Columnar Compression)
It is shares some part along with data storage of the Exadata storage cell, which is used to cache SQL query output helps in faster processing of frequently used queries
It is monitored using the below commands
cellcli -e "list flashcache"
cellcli -e "alter flashcache size=512G"
cellcli -e "list metrics where objecttype=flashcache and objectname='cd_01'
cellcli -e "alter flashcache cd=cd-01 size=200G
cellcli -e "list flashcache content cd=cd_01
cellcli -e "alter flashcache cd=cd_01 policy=Lru" // this is used for cache evictions
different policy are LRU,MRU,LFU,MFU
flash cache evictions are recorded in Exadata system AWR report
caching a frequently updated table in flash cache is of not use it will be lead to stale data
flash cache is auto managed , how ever we can manually control the flash cache using the command cell_flash_cache_keep/cell-flash_cache_none
Suppose if my table size is larger than flash cache you can plan for table partioning , however HCCC is there to compress the table
what is the tool available to check the exadata optimization?
exacheck
exawatch
OEM
steps to create a Cell Volume in Exadata using CELLCLI commands:
create disk -> physicalvol-> logicalvol -> volgroup -> add to grid disk -> then disk group
Step 1: Connect to the Storage Cell
$ ssh root@<storage_cell_ip_address>
Step 2: Start the CELLCLI utility
# cellcli
Step 3: Create a Grid Disk
CellCLI> CREATE CELLDISK ALL DISK <disk_path>
Step 4: Create the Physical Volume
CellCLI> CREATE PV ALL
Step 5: Create the Volume Group
CellCLI> CREATE VG <vg_name> DISK <disk_path>
Step 6: Create the Logical Volume
CellCLI> CREATE LV <lv_name> SIZE <size_in_GB> VG <vg_name>
create grid disk
CellCLI> CREATE GRIDDISK ALL PREFIX=<prefix> LV=<vg_name>/<lv_name>
add grid disk to disk group
CellCLI> ALTER DISKGROUP <dg_name> ADD GRIDDISK ALL PREFIX=<prefix>
Which protocol is used by ASR to send notifications?
SNMP Simple Network Management Protocol.Exadata ASR stands for "Automated Service Request" and is a feature of Oracle Exadata that enables automated and proactive support services
When Exadata ASR is enabled, the system automatically sends diagnostic information to Oracle Support in the event of a hardware failure or system issue. This information includes detailed logs and configuration information, allowing Oracle Support to quickly diagnose and resolve the issue.
What are the options to update cell_flash cache for any object?
cell flash cache is default enabled on exadata , if not we have to enable it manually using cellcli utility
#cellcli -e list cell detail
#cellcli alter cell flashcachemode=writeback
ALTER TABLE my_table CELL_FLASH_CACHE_KEEP;
ALTER TABLE my_table CELL_FLASH_CACHE_DEFAULT;
ALTER TABLE my_table CELL_FLASH_CACHE_NONE;
KEEP: Data blocks of the table should be kept in memory, even if the system needs to free up memory for other operations.
DEFAULT: This option specifies that the caching behavior should be determined by the system's default caching policy.
NONE: This option specifies that the data blocks for the table should not be cached in memory.
What is the default size of the smart flash log?
512MB per module.Each storage cell having 4 modules so its 4X512 MB per CELL
What is cellcli?
cellcli – It is a cell command-line utility. We can manage cell storage with the use of cellcli utility. We can say it’s a utility to administer cell storage.
CELLCLI-ALTER CELLCLI-CREATE CELLCLI-DROP CELLCLI-LIST
What is EHCC?
EHCC is Exadata Hybrid Columnar Compression which is used to compress data in the Database.Hybrid Columnar compression, also called HCC, is a feature of Exadata which is used for compressing data at column level for a table.
By default flash cache uses LRU algorithm
12. Types of EHCC?
Query Low/Query High/Archive High/Archive Low
In Oracle's Exadata Hybrid Columnar Compression (EHCC), Query Low, Query High, Archive Low, and Archive High are different compression levels that can be applied to different types of data in a table, based on their access patterns and usage.
Query Low: This compression level is suitable for data that is frequently accessed, and where compression ratios of 2x or higher can be achieved. It is best suited for data that is frequently queried and updated, and requires fast response times
Query High: This compression level is optimized for data that is less frequently accessed and can achieve higher compression ratios (4x or higher). It is best suited for data that is primarily queried and not frequently updated.
Archive Low: This compression level is suitable for data that is not frequently accessed but needs to be retained for legal or regulatory reasons. Archive Low compression is optimized for maximum storage efficiency and can achieve very high compression ratios (10x or higher).
Archive High: This compression level is optimized for data that is not frequently accessed, but needs to be retained for long periods of time for compliance or other reasons. It is best suited for historical data that is rarely queried. Archive High compression can achieve the highest compression ratios (20x or higher),
Which package can be used to estimate the compression ratio of the table?
DBMS_COMPRESSION
Background services of Cell Server?
MS: Management Server
cellsrv: Cell Server
RS: Restart Server
what is RS Restart Server?
Restart Server (RS) utility provides a simple and efficient way to restart a single or multiple database servers in an Exadata Database Machine, ensuring that the restart process is properly handled and that any dependent components are also restarted.
what is MS: Management Server?
Oracle Exadata, MS or Management Server refers to the component of the Exadata Database Machine architecture that is responsible for managing and monitoring the entire system.
The Management Server is a critical component of the Exadata Database Machine architecture that provides a unified view of the system, allowing database administrators to manage and monitor all the components of the system from a single interface. It provides essential functions such as configuration management, monitoring and performance management, patch management, and security management.
How to replace faulty HDD in Exadata Storage?
All the HDD are hot-swappable so if we are using proper redundancy then we can directly remove and replace the new HDD.
Storage software will take care of all the stuff in the background after replacing the HDD.
Exadata uses 2 types of redundancy normal and high , normal uses 2 mirror copies and high uses 3 mirror copies in the storage servers
How many disks come within a storage cell?12
What is the purpose of the spine switch?
Spine switch is used to connect or add more Exadata machines to the cluster
How to migrate the database from the normal setup to Exadata?
Their many methods we can use to migrate DB to Exadata. Below are some of them.
Export/Import
Physical Standby
Logical Standby
Transportable Tablespace
Transportable Database
Golden gate
RMAN cold and hot backup restoration
Oracle Streams
The use of the migration method totally depends on source setup as well as downtime consideration.
Exadata shutdown and start-up procedure
Shutdown Procedure:
Stop Database and Listener
Stop Cluster
Shutdown Database Servers
Shutdown Cell Storage
Shutdown all the switches
Remove powers from PDUs
The start-up procedure would be in reverse order.
How many database servers come in 1/8th rack and quarter rack?2
How many cell storage comes in full rack Exadata machine?14
Can we use a flash disk as an ASM disk?Yes
Which protocol is used for communication between the database server and storage server?iDB protocol
Which OS is supported in Exadata?
Database servers have two options for OS either Linux or Solaris which can be finalized at the time of configuration. Cell storage comes with Linux only.
What is ASR?
ASR is the tool to manage the Oracle hardware. The full form of ASR is the Auto Service Request.
Whenever any hardware fault occurs ASR automatically raises SR in Oracle Support and sends a notification to the respective customer.
How to integrate Exadata with OEM 12c?
Install OEM agent on DB server
Launch auto-discovery with the use of One Command XML file
Specify the required credentials for all the components
Review Configuration
Complete the setup
How to upgrade the firmware of Exadata components?
It can be done through ILOM of DB or Cell server.
\Where we can define which cell storage can be used by a particular database server?
CELLIP.ORA file contains the list of storage server which is accessed by DB server.
What are the Exadata Health check tools?
Exacheck
sundiagtest
oswatcher
OEM 12c
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