It is impossible to search user and unable to create local user at the "Manage"->"Users" part in the Identity and Access Manager which is integrated with LDAP. And got the error message in the server.log file like below:
2021-04-02 14:37:48,342 ERROR [org.keycloak.storage.ldap.idm.store.ldap.LDAPOperationManager] (default task-124) Could not query server using DN [ou=Level 2,ou=User Accounts,DC=xxaa,DC=yyysss01,DC=com] and filter [(&(cn=username)(objectclass=person)(objectclass=organizationalPerson)(objectclass=user))]: javax.naming.AuthenticationException: [LDAP: error code 49 - 80090308: LdapErr: DSID-0C090453, comment: AcceptSecurityContext error, data 568, v3839 ]
There was a problem in a provider in the "User Federation" part in the Identity and Access Manager when pushing "Test authentication" button in its "Settings" tab.
In detail, getting the error messages like below:
Release : 10.6
Component : CA Service Virtualization
In this case, several providers are defined in the User Federation part in the Identity and Access Manager.
And only one provider includes the problem.
By disabling the provider which had problem solved the problem.