how to configure apacheDS Ldap with the appian? In general any Ldap with Appian.

You will have to update the spring-security-03-auth-mgr.xml file with spring-security-03-auth-mgr-override.xml file (add a new file) and configure your LDAP settings there. This file is under \\appian72\\ear\\suite.ear\\web.war\\WEB-INF\\conf\\security folder.
The example given in the above link should help.
You also would require LDAP sync plugin to snyc users from yoru LDAP provider into Appian.

If you are trying to use your LDAP system for authentication then you are on the right track. Appian utilizes Sprint Security as its authentication framework and the documentation you were looking at has an example of configuring Spring Security to allow users to login with their LDAP credentials.

forum.appian.com/.../Authentication

If you are trying to sync users in Appian with those in your LDAP system I would suggest taking a look at the "LDAP User Profile Sync with Usernames" smart service plugin in the Shared Components.

@sathya and @eric, i have few general interest questions :
As we have two authentication-provider in spring-securuty-03-....xml file
1) appianAuthenticationProvider
2)ldapAuthenticationProvider

suppose say i have user X in LDAP but not in appian and now i am trying to login to appian using X credentials
is User X will have permission to log into the system? or
is it compulsory that we need to sync this user into our appian?
Where search will happend first in appian or LDAP?

Suppose we have multiple LDAP server then we need use a space between each LDAP server, such as: value="ldap://serverA:389/DC=abc,DC=uk ldap://serverB:389/DC=abc" in this case
my assumption is diffrent ldap are on diffrent machine. am i right?
if yes then how we will provide diffrent userDn and Password.

1. You need to have the user account in your LDAP system and Appian. Spring Security will authenticate the user against LDAP, but will fail to log the user into Appian as there is no user account. You will probably want to do one of the following:

Create Appian user accounts in a scheduled process based on an LDAP query by utilizing the "LDAP User Profile Sync with Usernames" smart service plugin in the Shared Components.

Create Appian user accounts during the authentication process once it is determined that the user has authenticated, but they do not have an Appian account. You would need to write a custom method and integrate it into your Spring Security setup to do this.

Determining which of those to use really depending on your specific requirements.

2. One way to provide a different userDn and Password would be to set the serverA and serverB entries into two separate authentication providers.