What do you mean by LDAP failover?
If you are talking about LDAP as a target resource, you essentially configure IM to talk to a load balancer ./ directory proxy server which is in front of the ldaps amongst which you want failover. That way, any one ldap server coming down is transparent to IM. Backend ldaps will naturally have replication running on them, etc.
Ankush
http://www.iamcg.net
You can use the native JNDI failover feature, which is based on multiple values in java.naming.provider.url
See http://java.sun.com/products/jndi/tutorial/ldap/misc/url.html#MULTI
The tricky part is to make IDM build such list, this can be achieved by extending the standard LDAPResourceAdapter and overloading LDAPResourceAdapterBase.getContextEnv (see REF kit).
Another way is to rely on the fact that IDM will simply concat the baseContext to the base URL => just add you failover url after the baseContext (use space, not carriage return as separator) :
<baseContext> ldap://<failoverHost>:<failoverPort>/<baseContext>