While starting LDAP server, we receive below error messages and LDAP doesn't start up. 

GLPRDB111E The server is unable to use the username and password combination for the DB2 instance owner in the configuration file to establish a connection to the database.
GLPSRV064E Failed to initialize be_config.

This could be a case where DB2 user password got expired and a new password reset needs to be performed along with update of the DB2 user password in ibmslapd.conf file. 

Resolution: 

Step 1: Check connectivity to Database. Connect to DB2 Instance user configured to LDAP Instance and check for any errors. 

db2 connect to <database instance user <username> using <user password>

Step 2: Validate if there is any message shown below. Incase yes, then proceed to modify DB2 user password. 
SQL30082N Security processing failed with reason "1" ("PASSWORD EXPIRED").
SQLSTATE=08001 

Step 3: Upon modifying DB2 user password, update ibmslapd.conf file, with new password. Verify the attribute "ibm-slapdDbUserPW " in ibmslapd.conf file and update the new password. Update the password in same text format rather in any other encrypted format. 
 
Step 4: Restart LDAP servers to validate the logs.