How the okd/openshift cluster can be used by multiple users simultaneously?
How can this problem be eliminated so that two users can parallelly use the cluster?
AFAIK, the OKD session is saved in $HOME/.kube/config by default. So it depends on a OS account session. If you'd like to use at the same time, then you should use different OS account each other. OR you should run oc login --config context_file_path per each execution for saving session to different context file. Refer Loading and Merging Rules for more details.
Note: Both User1 and User2 are configured with LDAP, is this creating problem?
No. Identity provider configuration does not affect this.
You should not share user accounts in this way. Each person who is logging in to the cluster should using a command-line client be doing so under their own linux uid against their own home directory. Sharing user accounts is a security vulnerability and removes your ability to track who is doing what.
kubectl and oc take this as a prerequisite, which is why you're running into this issue.