Why does a VXLAN offer greater VM mobility and availability in plain English! [closed]

I came across this statement

Since VXLAN is a logical L2 layer network running on top of a physical L3 layer network inside the data center, the latter is independent of the former. In other words, no device of the physical network has its configuration dependent on the configuration of any part of the virtual network. This provides the freedom to locate the computing and/or storage nodes belonging to a particular client in any physical segment of the data center network. In turn, this helps to locate those computing/storage resources based on performance and load balancing considerations. This results in greater VM mobility and availability

ISC2 Official CCSP Student Version p 480

As you can see, how does working at Layer 3 – which I assume is IP tunnelling contribute to this flexibility??

Can’t remove “synchronizing/suspect” database after removed from availability group Sql Server 2019 Enterprise

I’ve removed a db from a synchronous availability group.The db shows "synchronizing/suspect" as it should. I’m trying to remove this database cannot. I have tried:

DROP DATABASE [db1]; 

but get "Cannot drop database "db1" because it is currently in use.". even though their are no sessions using this database.

ALTER DATABASE [db1] SET OFFLINE; 

but get "ALTER DATABASE failed because a lock could not be placed on database ‘db1’. Try again later."

ALTER DATABASE [db1] SET SINGLE_USER WITH ROLLBACK IMMEDIATE 

but get "ALTER DATABASE failed because a lock could not be placed on database ‘db1’. Try again later."

ALTER DATABASE [db1] SET EMERGENCY; 

ALTER DATABASE failed because a lock could not be placed on database ‘db1’. Try again later.

This is a 24/7 production db and restarting is not a good option.

Any advice?

Failover an Availability Group during a backup

This is a scenario I hope won’t happen, but if I was to perform a manual failover on an availability group halfway through a database backup will this cause the backup to fail or would it continue? I’ve been looking through MS documentation but can’t find this specific case.

I’m running SQL 2017 in an active – active environment with the listener in a third location. (synchronous commit)

(Backups are utilizing the Ola Hallengren scripts)

Availability Group- Redo Rate displayed on AG Dashboard vs Perfmon counter

I am bit confused on checking the metrics for REDO Rate KB/Sec from Always on AG dashboard which for some scenarios matches with perfmon counter Database replica : Redone Bytes/Sec ( hopefully its correct counter for redo rate via perfmon) and sometimes not at all.

Most of the times when there is lot of activity ongoing, my belief is that AG dashboard and DMV shows REDO rate for e.g. 40 MB/Secs at given time which matches with perfmon counter.

However during less activity time or nothing much to send over to sec, REDO Rate on Dashboard and dmv seems to be showing incorrect values compared to perfmon counter.

Not able to understand which value is correct and how to analyze. Any idea why or is it bug in dashboard?

SPN for Availability group(AG) listener for SQL Server 2016

Requesting some inputs..

We have a 2 node SQL 2016 Availability group configured and apps currently use primary replica for connection. We are now planning to use listener instead. Questions is, how to make sure we are using kerberos authentication for application connectiions?. Is it mandatory to manually register SPN for the listener? or is it automatically created?. is this a one time activity?. How to make sure SPN is registered automatically for the listener when the AG restarts or failover to second node?. Appreciate all the responses.

How to configure Oracle traffic director for full site failover to have high availability?

I have two server system, each server having both apache tomcat server(deployed web app) and oracle 11g database server. The database on the two server is synchronised by oracle data gaurd for high availibility. tomcat Web servers is running individually on each server system with no load balancing. One server acts as primary server and other server acts as redundant server.

Usually for any failure on primary server, I have to manually change the IP/Domain name to access the other server.

I have came across Oracle Traffic director which may solve my isssue to switch any client request to redundant server in case of failure of primary server. Since I am new to oracle traffic director, can any one guide me to configure otd for full site failover?

behavior of a Sql Server availability group listener and a jdbc client during a failover?

i have a question about the behavior of the AG listener during a failover… when the failover happens, I realize that all the connections on both primary and secondaries are closed.

if the client apps are using one of the blessed client libraries (such as microsoft jdbc > 6.0) they will then start immediately trying to reconnect to the ip addresses associated with the listener. But what happens during the 10 second period (or whatever it is) for the failover to complete? Might a client successfully get a connection, only to get a fatal error message when it tries to use it? Or is something done to ensure that no client will get a connection successfully during failover itself, so that that when a client does successfully get a connection, it is actually usable?

(Also, specifically for a java client using a recent microsoft jdbc driver, does it try only once per getConnection() call? Or will it keep polling until a logintimeout is hit?)

I realize i’m mixing questions about server behavior with client library behavior but I’m trying to understand the whole scenario; thanks.

Resource Hosting Subsystem was terminated which caused Availability group to fail

The following error was occurred in cluster events and the availability group was failed which resulted the databases in non-synchronizing state.

A component on the server did not respond in a timely fashion. This caused the cluster resource ‘AG’ (resource type ‘SQL Server Availability Group’, DLL ‘hadrres.dll’) to exceed its time-out threshold. As part of cluster health detection, recovery actions will be taken. The cluster will try to automatically recover by terminating and restarting the Resource Hosting Subsystem (RHS) process that is running this resource.

Please help me to find the root cause (A component on the server did not respond in a timely fashion).

Thanks

Sync logins and Agent jobs across all replicas in Distributed Availability Group

I am using dba_CopyLogins stored proc to sync logins on replicas in Distributed Availability group , but the database level permissions are not transferred due to database sync operation is going on.. Is there any way to sync all logins and permissions from global primary to Forwarder and other replicas? also how to copy agent jobs?

How does Automatic Seeding work – Always On Availability Group

I found only these two statements from BOL regarding this Initial Data Synchronization method:

Link 1

Automatic seeding uses the log stream transport to stream the backup using VDI to the secondary replica for each database of the availability group using the configured endpoints.

Link 2

During automatic seeding, SQL Server performs a backup over the network for initialization.

Looking into SQL Server Error logs of both primary and secondary replicas, these two logs caught my attention:

On primary replica

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On secondary replica

enter image description here

My question is related to the working nature of automatic seeding, namely where does taken backup is stored before restoring on the secondary replica?