The action that must first be performed to ensure that there are no issues with Horizon LDAP replication within the Pod is to execute repadmin.exe/showrepl localhost:389. This command will display the replication status of the local Connection Server instance and show any errors or warnings that might affect the replication process1. The administrator should run this command on each Connection Server instance in the Pod before upgrading them in parallel, and resolve any issues that are reported.
The other options are not valid or feasible because:
Executing ViewDBChk.cmd --scanMachines will not check the Horizon LDAP replication status, but rather scan the vCenter Server inventory for virtual machines that are managed by Horizon and report any inconsistencies or errors2. This command is useful for troubleshooting virtual machine issues, but not for verifying LDAP replication.
Executing vdmexport.exe -f Myexport.lDF will not check the Horizon LDAP replication status, but rather export the Horizon LDAP configuration data to a file named Myexport.lDF3. This command is useful for backing up or restoring the Horizon LDAP data, but not for verifying LDAP replication.
Executing vdmadmin.exe -S will not check the Horizon LDAP replication status, but rather display the health status of the Connection Server instances in the Pod4. This command is useful for monitoring the Connection Server performance and availability, but not for verifying LDAP replication.
References:
Repadmin Examples1
ViewDBChk Tool2
Back Up Horizon Configuration Data3
Display Health Status Information4