Automatic Database Failover

What is the best way to do automatic Failover in 9i.
I have the DataGuard Environment setup. (Primary/Standby)
Can you use Transparent Application failover, Can
you use a script that monitors the Windows Service?
Help?

One of the new 10g R2 features is the ability to do fast-start failover to a standby database
http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14214/chapter1.htm#sthref234
Justin
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC

Similar Messages

Want to Buy SQL 2008/2012 standard edition to achieve Database failover

Hi Team,
We want to know exact part code details to procure 2 nos Sql 2008/2012 standard edition server to installed on "Window 2012 R2 Standard Edition, Factory installed, no media, 2 socket,2 VMs, No client" Server.
I have Access control system application (Main-Standby) on which we need Automatic database failover by using SQL Standard server. Application vendor has suggested us to procure 2 nos of Microsoft Sql 2008/2012 standard edition server.
If possible then please let me know exact part code details of Sql 2008 and 2012 standard edition server which doesn't have any issue to installed on above said server edition.
Thanks,
Vishal

Hi Vishal,
Unfortunately, we do not deal with part codes, I request you to check the below link as this is not the correct forum.
http://www.microsoft.com/en-in/server-cloud/products/sql-server/Support.aspx
Perhaps you could post you question on the SQL forum :
https://social.msdn.microsoft.com/Forums/sqlserver/en-US/home?category=sqlserver
Regards,
Mekh.

8.1.5.-automate database shutdown:hepl needed

I have tried to setup the automate database shutdown by following Oracle Manual. When rebooting the Unix system(sun solaris 2.6), nothing could be recorded in the alert logfile. After manually starting up the database, alert logfile indicated always a crash recovery during the process.
Any suggestion will be appreciated on above problem!
Felix

Hi,
Below is the information from orclALRT.log:
There's a write/open error. At July 21, 21:00PM our backup is start to run.
Is it because the backup software locked some oracle's files ?
But after the error, the next morning July 22 the ORACLE instance is started with no error, even though user can't connect to the database.
TIA
Andi
Thread 1 advanced to log sequence 46212
Current log# 4 seq# 46212 mem# 0: E:\ORANT\ORADATA\ORACLE\REDO01.LOG
Sun Jul 21 21:38:26 2002
KCF: write/open error block=0x11072 online=1
file=1 E:\ORANT\ORADATA\ORACLE\SYSTEM01.DBF
error=27072 txt: 'OSD-04008: WriteFile() failure, unable to write to file
O/S-Error: (OS 33) The process cannot access the file because
another process has locked a portion of the file.'
DBW0: terminating instance due to error 1242
Instance terminated by DBW0, pid = 248
Mon Jul 22 03:00:04 2002
Starting ORACLE instance (normal)
Dump file E:\orant\admin\oracle\bdump\orclALRT.LOG
---------

Messages Stuck in Submission Queue after Database failover to DR site

Hi Everyone,
Yesterday Night we had a Database failover to DR site but emails were stuck in the submission queue to resolve we failed back the Database. We have Exchange 2010 SP3 Ru4 with Active-Active DAG across 2 AD sites.
After checking the connectivity logs on the Transport server i found out that the Transport server was trying to connect to the mailbox server where this database was residing directly instead of using the Transport servers in the 2nd site.
We have 4 more databases on the same server but for those databases there was no issues and the mail flow was working fine.
Only thing i checked is that we have about 700 GB of log files for this database. Could that can cause this issue.

Hi,
Thanks for your response.
I did not restart transport service. I assume restarting transport service might have resolved the issue.
But, i want to know the reason why this happened as we have stretch DAG so this can cause major outage in case more mailbox database fails over.
Removing the logs files is what i am thinking to do maybe within this week.

How to automate database startup/shutdown in RHEL4

Dear All
I have Oracle 10gR2 database on RHEL4.
If i want to automate database startup/shutdown with OS startup/shutdown,
Then where i need to update about dbstart.sh & dbshut.sh
I have already made entry in /etc/oratab as Y for database SID.
I am using Bourn Shell.
Thanks

You can refer to my post in my Blog
[Automatically StartUp and Shutdown an Oracle Database in Linux OS|http://kamranagayev.wordpress.com/2008/12/22/automatically-startup-and-shutdown-database-in-linux-os/]
Kamran Agayev A. (10g OCP)
http://kamranagayev.wordpress.com
[Step by Step install Oracle on Linux and Automate the installation using Shell Script |http://kamranagayev.wordpress.com/2009/05/01/step-by-step-installing-oracle-database-10g-release-2-on-linux-centos-and-automate-the-installation-using-linux-shell-script/]

Recover automatic database

STARTUP MOUNT
RECOVER AUTOMATIC DATABASE (The database automatically suggests and applies the necessary archived logs)
From which destination DB is looking for archivedlogs?
db_recovery_file_dest or log_archived_dest?

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 209715200 bytes
Fixed Size 1248140 bytes
Variable Size 79692916 bytes
Database Buffers 125829120 bytes
Redo Buffers 2945024 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1:
'D:\ORACLE\PRODUCT\TESTDB\TESTDB\DATAFILE\O1_MF_SYSTEM_352363BQ_.DBF'
SQL> select file# from v$recover_file;
FILE#
1
2
3
4
SQL> shutdown immediate;
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 209715200 bytes
Fixed Size 1248140 bytes
Variable Size 79692916 bytes
Database Buffers 125829120 bytes
Redo Buffers 2945024 bytes
Database mounted.
SQL> recover automatic database;
Media recovery complete.
SQL> alter database open;
Database altered.
SQL> select file# from v$recover_file;
no rows selected
It picked from db_recovery_file_dest
SQL> show parameter log_archive_dest;
NAME TYPE VALUE
log_archive_dest string
log_archive_dest_1 string
log_archive_dest_10 string
SQL> show parameter db_recovery
NAME TYPE VALUE
db_recovery_file_dest string D:\oracle\Product\Backups
db_recovery_file_dest_size big integer 2G

Sql Server Agent not starting automatically in failover in a clustered environment.

Hi,
We are running Sql Server 2008 R2 as a 2 node cluster in Windows 2008 R2
server. In the Sql Server Configuration manager we find that service of
the Sql Server(database engine) as got a start mode as manual being
an instance in the 2 node cluster. When the node in which the service is
running fails the the Sql Server service gets started in the other node. However
we find that the Sql Server Agent service(whose start mode is also in manual)
does not get started automatically in the other node along with the Sql Server
service.Why does the cluster service do not start Sql Server agent service as well.
Should we make the Sql Server agent service start mode to be automatic
instead of being manual as it is now? Thanking you in advance
Binny Mathew

Folks - the startup type of all clustered services should be set to manual - when you virtualize SQL Services, they are put in manual startup mode and this should not be changed. It is the cluster manager which starts the SQL and SQLAgent when a
failover happens (SQL does not start SQLAgent). If your SQLAgent doesn't start after a cluster failover, check the SQLAgent logs to see what the root cause of the problem is and rectify it. You should not change the startup type to "Automatic" -
leave it as manual
Satish Kartan www.sqlfood.com
I suspect that your clustered SQLAgent resource is currently NOT dependent on SQL resource. If not, make SQLAgent dependent on SQL resource, which will coerce SQLAgent to wait for the SQL resource to come online before it brings itselft (SQLAgent) resource
online, when a failover happens.
Satish Kartan www.sqlfood.com

Unexpected DAG mailbox database failover

Good evening
I am running a three node Exchange 2013 server environment in a stretched DAG configuration. I have been experiencing a problem recently whereby failover is occurring unexpectedly. Below is a brief description of the environment.
Site 1 (Head Office)
2 x Exchange 2013 CAS/MBX (dual role servers, lets call them A and B)
Both are members of the only DAG we have
They both have copies of the only mailbox database we have
Server A has activation preference 1
Server B has activation preference 2
Site 2 (Datacenter)
1 x Exchange 2013 CAS/MBX (dual role server, lets call it C)
C is a member of the same DAG as above
It hosts a copy of the same mailbox database as above
Server C has activation preference 3 (although I have configured it to never automatically activate a database copy)
Server C will only be actively used in a disaster scenario where we lose both A and B in the head office for whatever reason
So recently I have noticed that when the mailbox database is mounted and active on server A after a period of not more than an hour or two, the database is automatically moved to server B. This has happened 3 times now.
I find these informational alerts in the event viewer on server A.
Event ID 2136
Log Name: Application
Source: MSExchangeRepl
Date: 14/11/2014 16:01:03
Event ID: 2136
Task Category: Service
Level: Warning
Keywords: Classic
User: N/A
Computer: ServerA.domain.internal
Description:
Unable to communicate with the Microsoft Exchange Information Store service to coordinate log truncation for database 'Mailbox Database 1\ServerA' due to an RPC communication failure. Error: 3355381764
Extended error: Failed to open a log truncation context to source server 'ServerA.domain.internal'. Hresult: 0xc7ff1004. Error: Error returned from an ESE function call (-1305).
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="MSExchangeRepl" />
<EventID Qualifiers="32772">2136</EventID>
<Level>3</Level>
<Task>1</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2014-11-14T16:01:03.000000000Z" />
<EventRecordID>4381652</EventRecordID>
<Channel>Application</Channel>
<Computer>ServerA.domain.internal</Computer>
<Security />
</System>
<EventData>
<Data>Mailbox Database 1\ServerA</Data>
<Data>3355381764</Data>
<Data>Failed to open a log truncation context to source server 'ServerB.domain.internal'. Hresult: 0xc7ff1004. Error: Error returned from an ESE function call (-1305).
</Data>
</EventData>
</Event>
Event ID 3169
Log Name: Application
Source: MSExchangeRepl
Date: 14/11/2014 16:01:04
Event ID: 3169
Task Category: Service
Level: Information
Keywords: Classic
User: N/A
Computer: ServerA.domain.internal
Description:
(Active Manager) Database Mailbox Database 1 was successfully moved from ServerA.domain.internal to ServerB.domain.internal. Move comment: Managed availability system failover initiated by Responder=RpsDeepTestPSProxyFailover Component=RPS.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="MSExchangeRepl" />
<EventID Qualifiers="16388">3169</EventID>
<Level>4</Level>
<Task>1</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2014-11-14T16:01:04.000000000Z" />
<EventRecordID>4381655</EventRecordID>
<Channel>Application</Channel>
<Computer>ServerA.domain.internal</Computer>
<Security />
</System>
<EventData>
<Data>Mailbox Database 1</Data>
<Data>ServerA.domain.internal</Data>
<Data>ServerB.domain.internal</Data>
<Data>Managed availability system failover initiated by Responder=RpsDeepTestPSProxyFailover Component=RPS.</Data>
</EventData>
</Event>
Does anyone have any ideas as to why this might be happening or whether there are any additional troubleshooting steps I can take?
Regards

Hi George,
Agree with Jared, running CollectOverMetrics.ps1 script is a good choice to troubleshoot the issue.
Except this method, you can also refer to the following article to troubleshoot the issue with other useful information, like mailbox database replication status information, HighAvailability channel event logs..
http://technet.microsoft.com/en-us/library/dd351258(v=exchg.150).aspx
Best regards,
Niko Cheng
TechNet Community Support

9i Standby Database - Failover Question - REF 227196.1

Hi ,
Im researching the use of a Standby DB for out Production DB....
The Metalink DOC 227196.1 mentions that in failover , the Production going down , Standby becomes Primary and cannot be come Standby again , whereas with Switchover , they can be swapped as many times as you need for upgrades etc...
"The Difference between a Switchover and a Failover is, that after a Failover, the Standby Database becoming a Primary now, cannot switchback to become a Standby Database again. In Opposition a Switchover exchanges the Database Roles (The Primary becomes a Standby and the Standby becomes a Primary). Switchovers can be performed arbitrarily, a Failover only once."
If failover happens can someone tell me or point me in the right direction:
a) Can you config Failover to happen automatically?
b) If failover occurs , do you need to reconfig all the Primary/Standby DB again in the event that failover happens again?
c) Any clear step by step guide to config of standby... The Oracle docs whilst very good are robust and some "summary" steps would be great
thanks in advance
Stephen

HI,
Please check this link:
Physical Standby Database SWITCHOVER &amp; FAILOVER Operations | Talip Hakan Ozturk&#039;s ORACLE BLOG
Thank you

Publication is not listed in reolication monitor after manual database failover

Hi All,
I have three servers using which I have configured database mirroring and transactional replication with pull subscription.
ServerA--Publisher/Distributor/principal
ServerB--Subscriber
ServerC--Mirror
After failover now ServerB pulls the data from ServerC which is the new Principal andI have set the -PublishfailoverPartner as ServerC .
After the failover is performed I see subscriber is pulling transactions from ServerC and transactions are getting replicated but I cannot see the publication listed under new publisher(ServerC) nor under old publisher ServerA from replication
monitor.
What is the reason I cannot see the publications from replication Monitor. How will distributor know that ServerC is now the publisher.
Also I got the error when I executed below command for distribution agent. But still transactions are getting replicated after failover.
exec
sp_add_agent_parameter@profile_id
= 4,
@parameter_name =
N'-PublisherFailoverPartner',
@parameter_value =
N'ServerC
Msg 21806, Level 16, State 1, Procedure sp_MSvalidate_agent_parameter, Line 63
parameter -PublisherFailoverPartner. The value must be an integer. Verify that replication is installed properly and that sp_add_agent_parameter is invoked with a valid value.The agent profile creation process cannot validate the specified agent parameter
value: the profile_id 4 does not exist or it does not support the
Any inputs will be of great help.
Regards,
Raj
Raj

Refer to this: http://msdn.microsoft.com/en-us/library/ms151799.aspx

Standby database failover flashback restart as standby gap 1-100

Hi,
I have setup a physical standby database for a 3 node RAC primary database and configured the database to run in MAXIMUM AVAILABILITY mode. Both the primary and standby databases use ASM for managing the IO. I have enabled FLASHBACK ON on both the databases.
I did failover to standby database with primary db SHUTDOWN for doing some testing. After testing is done, I flashbacked the (standby, currently primary)database to the point when it became primary and start it as standby again and the old primary as primary.
Following are the steps:
Failover steps
.Shutdown the primary database
To finisish the recovery at standby
SQL>alter database recover managed standby database finish;
To start as primary
SQL>alter database commit to switchover to primary;
do some DML on the new primary
SQL>flashback database to scn <standby_became_primary_scn>;
SQL>alter database create standby controlfile as '/backup/standby.ctl';
Changed the spfile to point control_files to '/backup/standby.ctl';
Restarted the standby db in mount mode and
created the required stanbdy logs on it.
Then issued
SQL>alter database recover managed standby database using current logfile disconnect;
I have the following message in v$dataguard_status at standby db;
Fetching gap sequence in thread 1 branch(resetlogs_id) 653234404, gap seq 1-100
DBID 2651011616 branch 653234404
GAP - thread 1 sequence 1-100
FAL[client]: Failed to request gap sequence
FAL[client]: All defined FAL servers have been attempted.
The same error is found in alert log file also.
The status of the varioud managed standby db are as follows.
SQL> select process, status from v$managed_standby;
PROCESS STATUS
ARCH CLOSING
ARCH CLOSING
ARCH CLOSING
MRP0 WAIT_FOR_GAP
RFS IDLE
RFS IDLE
RFS IDLE
RFS IDLE
RFS IDLE
RFS IDLE
RFS IDLE
PROCESS STATUS
RFS IDLE
RFS IDLE
RFS IDLE
RFS IDLE
15 rows selected.
SQL>
Could you please help me how to resolve the above error.
Thanks,
Sreekanth

Sreekanth,
I think your steps are right on for your requirement, except instead of
alter database create standby controlfile as '/backup/standby.ctl';
you can do this:
ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
(although perhaps it achieves the same thing internally but you don't need to repoint to new controlfile).
So far as the GAP - thread 1 sequence 1-100
Let me guess, your current sequences are probably well ahead of this reported gap?
If so, this is a bogus gap in a sense that your standby has long ago applied them, but for some reason standby controlfile gets a little confused and starts asking for them again.
I have had this issue and opened multiple TAR's with Oracle since 10.2.0.1, got a few patches and advises to upgrade, but still occasionally get it now in 10.2.0.3
I strongly believe this is related to combination of RAC (i.e. multiple threads of redo) and dataguard.
It is also pretty hard to reproduce (I have not figured out how to reproduce this reliably, if you have, let me know), so I can understand why Oracle has so far been unable to fix this.
Anyway, the workaround is to re-create standby controlfile with a copy generated on primary, and move it in place of the existing (and confused) controlfiles on standby.

Automatic database activation

hi,
Suppose we have two mailbox servers: Node 1 and Node 2 in a DAG with two databases: A and B.
A is mounted on node 1 and B is mounted on node 2.
Now Node 2 suffers a hardware failure, a windows failure or lost its connectivity to databases (their databases are located in SAN for instance); will the passive copy of database A located on Node 2 get automatically mounted or I need to run some command?

Hi ,
As per your scenario , database A will remain mounted on the node 1 because we have faced the failure only on node 2.
On node 2 we have only one active copy which is called database B.So during failure database B will get automatically mounted on the node 1 unless the database copy B doesn't have any database level activation block.
Thanks & Regards S.Nithyanandham

Problem with automatic database startup (dbora)

I'm running Linux RHEL5 with 10g v2 database. For some reason the script fails to start the database. But when I logon as user Oracle, I can run dbstart ORCL and the database starts up fine. Below is what I see when the script runs. Not sure why the connection is refused. Thanks in advance for your help.
Starting dbora: + ORACLE_HOME=/u01/app/oracle/product/10.2.0/db_1
+ ORACLE=oracle
+ PATH=/sbin:/usr/sbin:/bin:/usr/bin:/u01/app/oracle/product/10.2.0/db_1/bin
++ hostname
+ HOST=Linux10gVM.norris.intra
++ uname
+ PLATFORM=Linux
+ export ORACLE_HOME PATH
+ rsh Linux10gVM.norris.intra -l oracle /etc/rc5.d/S99dbora start ORCL
Linux10gVM.norris.intra: Connection refused
+ pause ‘Press any key to continue...’
+ read ‘~p’ ‘Press any key to continue...’

AHA...just as I expected!!!
My automatic 11g1 start up and shutdown quit working in 3/2009
after working for months!
I suspected pam.d
Here it is : http://blog.fourthirty.org/?cat=45
#%PAM-1.0
# For root login to succeed here with pam_securetty, "rsh" must be
# listed in /etc/securetty.
auth required pam_nologin.so
auth required pam_securetty.so
auth required pam_env.so
# auth sufficient pam_rhosts.so
auth sufficient pam_rhosts_auth.so
account include system-auth
session optional pam_keyinit.so force revoke
session include system-auth
session required pam_loginuid.so
more www.ask.com search for "dbstart pam.d"
LMKIII (root) ~ [999]>cd /var/log
LMKIII (root) /var/log [1000]>cat secure
Apr 17 18:43:57 LMKIII sshd[2176]: Server listening on 0.0.0.0 port 22.
Apr 16 18:44:10 LMKIII rshd[2473]: PAM unable to dlopen(/lib/security/pam_rhosts_auth.so): /lib/security/pam_rhosts_auth.so: cannot open shared object file: No such file or directory
Apr 16 18:44:10 LMKIII rshd[2473]: PAM adding faulty module: /lib/security/pam_rhosts_auth.so
Apr 16 18:44:11 LMKIII rshd[2473]: pam_rhosts(rsh:auth): denied access to [email protected] as oracle
Apr 16 18:44:11 LMKIII rshd[2473]: pam_unix(rsh:session): session opened for user oracle by (uid=0)
Apr 16 18:45:11 LMKIII rshd[2473]: pam_unix(rsh:session): session closed for user oracle
Apr 16 18:49:07 LMKIII kdm: :0[2881]: pam_unix(kdm:session): session opened for user oracle by (uid=0)
Apr 16 18:50:41 LMKIII su: pam_unix(su-l:session): session opened for user root by oracle(uid=503)
Apr 16 18:54:46 LMKIII su: pam_unix(su-l:session): session closed for user root
Apr 16 18:54:49 LMKIII kdm: :0[2881]: pam_unix(kdm:session): session closed for user oracle
Apr 16 18:55:01 LMKIII sshd[2176]: Received signal 15; terminating.
Apr 16 18:56:55 LMKIII sshd[2171]: Server listening on 0.0.0.0 port 22.
Apr 16 18:57:08 LMKIII rshd[2473]: PAM unable to dlopen(/lib/security/pam_rhosts_auth.so): /lib/security/pam_rhosts_auth.so: cannot open shared object file: No such file or directory
Apr 16 18:57:08 LMKIII rshd[2473]: PAM adding faulty module: /lib/security/pam_rhosts_auth.so
Apr 16 18:57:09 LMKIII rshd[2473]: pam_unix(rsh:session): session opened for user oracle by (uid=0)
Apr 16 18:58:09 LMKIII rshd[2473]: pam_unix(rsh:session): session closed for user oracle
Apr 16 18:59:26 LMKIII kdm: :0[2880]: pam_unix(kdm:session): session opened for user oracle by (uid=0)
Apr 16 19:00:31 LMKIII su: pam_unix(su-l:session): session opened for user root by oracle(uid=503)
Apr 16 19:01:50 LMKIII su: pam_unix(su-l:session): session closed for user root
Apr 16 19:02:23 LMKIII su: pam_unix(su-l:session): session opened for user root by oracle(uid=503)
Apr 16 20:48:14 LMKIII sshd[4117]: Address 194.80.134.6 maps to no-reverse-defined.ja.net, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Apr 16 20:48:14 LMKIII sshd[4117]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=194.80.134.6 user=root
Apr 16 20:48:16 LMKIII sshd[4117]: Failed password for root from 194.80.134.6 port 51090 ssh2
Apr 16 20:48:16 LMKIII sshd[4120]: Connection closed by 194.80.134.6
Apr 16 21:11:12 LMKIII sshd[4287]: Address 194.80.134.6 maps to no-reverse-defined.ja.net, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Apr 16 21:11:12 LMKIII sshd[4287]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=194.80.134.6 user=root
Apr 16 21:11:14 LMKIII sshd[4287]: Failed password for root from 194.80.134.6 port 53791 ssh2
Apr 16 21:11:15 LMKIII sshd[4290]: Connection closed by 194.80.134.6
Apr 16 21:28:54 LMKIII sshd[4383]: Address 194.80.134.6 maps to no-reverse-defined.ja.net, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Apr 16 21:28:54 LMKIII sshd[4383]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=194.80.134.6 user=root
Apr 16 21:28:55 LMKIII sshd[4383]: Failed password for root from 194.80.134.6 port 44904 ssh2
Apr 16 21:28:56 LMKIII sshd[4386]: Connection closed by 194.80.134.6

Scheduling Automatic Database objects comparison through Oracle CHange Mana

HI,
I need to compare some schemas for two databases regularly to make sure that the databases are in sync state.Could you guys pls tell me if there is any option/way through which i can do the automatic scheduling to compare the DB objects of the two databases.
Your help would be highly appreicated.
Many Thanks

TOAD

Why does 1 mail database failover

We have 2 Exchange 2013 servers in a DAG, each server hosts 3 databases. 5 of the 6 databases have copies on both servers, the 6th is a test one which we do not want to replicate.
One of the databases keeps failing over to the other server, it lists it's usual host server as its preferred server and the passive copy as its second choice yet it repeatedly goes into failover while the others remain on their host as they should.
The databases are all pretty close to the same size with the same number of mailboxes.
Does anyone have any idea what could be causing this?

Looking through event logs, the only error I see is this, found in
Application and Services Logs > Microsoft> Exchange > HighAvailability > Operational
An error occurred while trying to select database copy 'Database' on server 'server.domain.com' for possible activation. The following checks were run: 'IsHealthyOrDisconnected, IsCatalogStatusHealthy,
CopyQueueLength, ReplayQueueLength, IsPassiveCopy, IsSeedingSource, TotalQueueLengthMaxAllowed, ManagedAvailabilityAllHealthy, ActivationEnabled, MaxActivesUnderPreferredLimit'. Error: Database 'datsbase' is already hosted on target server 'server'.
Just before this was an information event saying it was initiating the move, no explanation why, no events for 30 minutes before this.

Automatic Database Failover

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