How SCAN Works in RAC? |
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- เผยแพร่เมื่อ 6 ก.พ. 2025
- In this episode of daily DBA, I would like to present you with #SCAN listener concept inside #Oracle RAC and how it functions!
How SCAN works inside Oracle RAC?
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Hurreh thank you so much sir🕺
@@sandeepsindhu346 congratulations bro
Mail sent sir
in the database thre is MMON process which actually calculates the load on the database and save it to the service metrics and then the LREG process communicate the service metrics to the SCAN listener. using the service metric information , the SCAN listener decides which node has the less load.
Good and superb explanation about scan
i have no word for your talent explanation, Mr.Arun you are a great teacher
Keep watching
the perfect, beautiful example for SCAN Thank you so much Arun, after this example, I get a clear idea about SCAN, as per my knowledge (searched in google) Load Balance Advisory is one whos is going to help the scan listener for load balancing
wao Perfecto, muy bien explicado, yo quería encontrar una explicación sobre como SCAN funcionaba y gracias a Dios encontré este Canal. thank you very much DBA Genesis.
On Oracle RAC environment Load Balancing is something which is critical for distribution of connections between the servers we have. Load Balancing Advisory (LBA) is one of the key components for SCAN listener to decide the best instance for the new incoming connection request.SCAN using details from LBA, identifies the load on each node in the setup and routes the request xyz to the node which has least load.
One of the simply beautiful explanation of SCAN I've ever seen. Kudos Arun!
We love it when our videos help DBAs across the globe!
I always say our database administration is very much analogous/connected to most of our lives. And sir you have presented in such a way that, no one can forget this concept with the airport analogy taken. Awesome explanation. Story remains in mind forever :)
(LBA) LOAD BALANCING ADVISOR- PMON of each node records and updates the load in LBA it's register in the given example
Thanks friend.I have an interview and don't have time for challenge 🤭🤭
you are doing an excellent service. God bless!
Thank you!
The Best explanation of RAC SCAN LISTENER any day! Understood it much more better than before.
Load Balancing Advisory (LBA) is the answer you are searching for. LBA helps SCAN LISTENER to balance load across the instances in Oracle RAC. Load Balancing Advisory(LBA) is intelligent enough to advice for connection load balancing based on data collected by PMON of all the instances. LBA is definitely mandatory for SCAN listener in Oracle RAC.
what a beautiful explanation..no words !!!
Glad you liked it
so beautiful example to explain rac scan ip
Just wow... Awesome explanation from you.. Very simple with amazing example... I never understood so deeply from any video sir...
You are most welcome! Honoured to help you with the concept !!
I feel that I had just hit the goldmine, new fan of DBA Genesis. Thank You.
Most welcome buddy!
I had given a Interview yesterday the interviewer asked me a question How SCAN works I gave a example similar to the one explained and I told that there is a Load Balancing Advisor (LBA) which has all the details of the load on each node and it routes the connection to the node with least load. It gets the information of the load from the PGA's/client connections to the node and the LBA is update by the PMON background Process.
But the interviewer was of the opinion that I have cooked up some new story about scan IP's which he never heard about.
Hahahaaa... Happens!
PMON registers with the listener when instance or DB starts .PMON process having/knowing all the load information of each instances of RAC .the Scan listeners will get the information from PMON process about the load of each instances
Oracle Net Services provides connection load balancing for database connections. The listener uses the load balancing advisory for connection load balancing.
LREG process which gets registered with the local listener has all the details of the load on each node which helps scan listeners to distribute the load equally.
Nice easily understandable , thanks arun :)
Keep watching
Very Good. Superb.
Thanks!!
Scan listener using details from LBA, identifies the load on each node in the setup and routes the request to node which has least load like node4.
In this case it happened to be node2 with least load or no load and the request is addressed by local listener on this node which helps request to establish a session on instance on node2.
That respected SCAN listener using details from LBA, identifies the load on each node in the setup and routes the request to node which has least load . PMON of each node updates details about each node in LBA .
Mast😄👍👍👍 trick to understand
Keep watching
Very good video and really simple! Especially for someone which is completely new to DBA knowledge.
What a explanation sir ...hatts off ❤️🙏
hi i follow your lectures they are very good i want to see your oracle rac tutorials
SCAN Listener use details from LBA, identifies the load on each node in the setup and routes the request to node which has least load.
Perfect
SCAN listener will check for the least loaded instance. It will then redirect the connection request to the local listener on the node where the least loaded instance is running. Eventually the client will be given the address of the local listener to make the connection with the database instance.
Great explained
Glad you liked it
Beautiful explanation 👍
Keep watching
Good explanation.
Glad you liked it
XYZ person in your example is local listener on each node who knows load/number of connections on the respective instances and provide these details to scan listener.
LBA decides to which local listener the connection to be re-routed from scan listeners and PMON updates the load on each node in LBA.
pmon process for each instances registers the database services with the default listerner on the local node. And with each scan listener which is specified by remote_listerner parameter.
basically client queries the dns to resole the scan name ,
and scan then selects the least loaded node
Note : - the client then directly connects to the dedicated server process on the least loaded node
It internally follows the round-robbin alogorithem for specifying load to connect to session which is having less sessions connected to
Scan always re-route the connection to local listener.
Decide to which local listener connection request to be re-routed.
PMON of each node record and updates the load in LBA ( Load Balancing Advisor)
Good one!
Those guys awesome.
In Oracle RAC, the Clusterware service stores information about the load balance in the Cluster Synchronization Services (CSS) daemon, which is responsible for synchronizing the cluster state across all nodes in the cluster.
Server Side Load balancing:
Scan Listeners connects to all instances with all listeners so that instances can spread their load balance advisories to all listeners. Listener uses the advisories to decide which instance should service client request. If listener know from advisories that its local instance is least loaded and should service client request then listener passes client request to local instance. If local instance is over loaded then listener can use TNS redirect to redirect client request to a less loaded instance means remote instance.
Thanks for sharing this info i had always doubt, I knew Pmon register will load the balnce at server level. . but Above that how it Balance . .Now i got it DNS. . .thanks . .
Thank you! keep watching!
Your videos are great ..you 🔥
Thank you so much 😀
awesome bro
Glad you liked it
PMON of each node records and updates the load in LBA and LBA decides to which local listener connection request to be re-routed. SCAN always re-routes connection request to local listeners.
LBA (introduced in 11g) is a memory area basically under shared pool, as PMON provides the statics to LBA
Any link please. I couldnt find anything in oracle docs.
Thank u sir wow explanation
Keep watching
REMOTE_LISTENER, LOAD BALANCE ADVISER and PMON.
SQL> alter system set remote_listener='SCAN-name:port-number' scope=both
LBA(Load balancing advisory) for check each node load & provide this node load detail to scan listener.
Load balancing advisor LBA ( LBA updated by PMON background process from each nodes) #dba_challenge
Hi arun what happen if password file is deleted from standby server? will there any impact sync with primary server?how will fix the issue?
Picked up your question for future episodes, will be answering it soon!
Load balancing advisor.PMON of each node update the load of the node to LBA
Xyz is none another local listener of the instance node, db instances and services would be registered with remote listeners or scan listeners, hence with the help pmon of the instance its updates the records and load on it in LBA , once LBA knows the status of each node's ,scan listeners would divert the request in round roubin manner to least bother node through local listener of the node, hence establishes a session on instance which has least lode node.
SCAN will use the Load balancing adviser and identifies load in each node in the cluster.
Hi Arun, LBA update the information to scan listeners, this information shared from local listener to LBA.
Suppose, if I have to set up a RAC with 4 nodes, how many SCAN IPs do I need?
3
LBA ( load balance advisor) ..
It will get least load node details with help of MDnS and pmon..
Hi, Could you please give some information about VIP in RAC... Thanks..
Check episode 22 for VIP
@@dbagenesissure...
LBA load balance adviser pmon on each node update the LBA about the load
He went from a Boeing 777 to an Airbus Beluga, nice.
Genius indeed
Our entire DBA community is Genius! Let's help our fellow friends join this DBA community!
If you could have explained litlle bit more about where VIP, Services, local listener and remote listener fits in above airport example , it would have been great
Load balance adviser will collect load information from each node using local listener and keep in load balance adviser. Scan listener will communicate LBA and get the least load information and then it will establish the connection with that node through local listener
I have one question , why only 3 scan !!! Why not 4 or 5 ????
Why don't you google it up and let us all know if it is possible or not?
This feature is called load balancing.
LBA.. Many people already have answered .. :)
Grid Load Balancing (GLB) Service
Once again thank you so much..
Load balance adviser.(LBA)
Integration of Oracle Listener with Load Balancing Advisory.
With the help of Load Balancer Advisory, Scan listener choose the node having less workload.
As part of Fast Application Notification (FAN) event transmission features, Oracle 10g RAC uses Oracle Notification Services (ONS) to communicate the status of cluster resources to all participating node applications in the cluster. In Oracle 10gR2, FAN added a new event type, SERVICE_METRIC, whose event payload contains information about the relative workload of each node in the RAC cluster, and this information Load Balancing Advisory uses to determine how to route new connections throughout the clustered database’s instances.
LBA is there. Load balance Advisory
Oracle traffic director and windows load balancer
LOAD BALANCING ADVISOR WITH THE HELP OF PMON COLLECT DETAILS PUSH TO CLIENT THEN CLIENT DECIDE IT.
Hi Arun, great going and enjoying your daily DBA show .I wanted to know from you and other sr dba,,s personal experience what is one of the rarest of rare crisis situation a DBA can experience in real-time like site crash or anything that hardly any DBA sees in their entire career which most of the DBA,s are scared of or the situation is very challenging .
Good one, I guess I would love to speak about one situation in upcoming episodes that all of you should know.
services or server pool
Load balance Advisory
LBA
And dns ki round Robin algo
Load balancing advisory process
And each node has its local listener also
Remote listener init parameter
How 3 disks for normal redundancy disk group is managing the heartbeat information from 15 node rac or 5 disks for high redundancy disk group is managing the same heartbeat among 15 node rac ... Please help @Arun..
Get your RAC architecture right, you will have the answer. Its a wrong question you are asking!
@@dbagenesisOLR is the right asnwer..?
Normal =1, External=3 & High= 5
LBA(Load Balance Advisor)
You are right buddy!
Connection load balancing
Tilt could be how to enter airport fly
LBA sir
Load balancing advisor
Management DB Sir
It Is Rac Scan IP method
The answer is LBA (Load Balancing Advisory)
Workload Management relies on the use of Services
(LBA) LOAD BALANCING ADVISOR
LBA ( advisor )
Load Balancer
LBA
Ocr and olr
VIP scan it's simple
Scan IP it is..
Hi Arun
Node VIP will maintain the current Load on the Host
Load balancer
VIP ip
pmon
Vip - virtual ip address that knows load balance of each original ip address of each host.
Load balancing advisor
Xyz is none another local listener of the instance node, db instances and services would be registered with remote listeners or scan listeners, hence with the help pmon of the instance its updates the records and load on it in LBA , once LBA knows the status of each node's ,scan listeners would divert the request in round roubin manner to least bother node through local listener of the node, hence establishes a session on instance which has least lode node.