database - DBMS_LDAP package, ACLs, dictionary statistics

Hi,

1)I'm upgrade from 11.2.0.2.0 to 11.2.0.3.0, and Configuration Assitant display this warning/recommendation message:

WARNING: --> Database contains schemas with objects dependent on DBMS_LDAP package.
.... Refer to the 11g Upgrade Guide for instructions to configure Network ACLs.
.
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Recommendations
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Oracle recommends gathering dictionary statistics prior to
upgrading the database.
To gather dictionary statistics execute the following command
while connected as SYSDBA:

and then a popsup appear, ask me to follow ahead by pressing Yes/No 

2)do you know  the meaning of:

DBMS_LDAP package
ACLs
dictionary statistics

thanks