ldap/autoregister is a SAP Parameter attribute which is used to control Enable LDAP auto registration information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
You can use this parameter to activate the automatic registration of the
SAP instance in an LDAP directory.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.