I upgraded the version to openldap 2.4.22 and now I could add the ldif file with the arl in with slapcat command
Previously the same was not working, so I guess the bug in 2.4.21 is fixed in 2.4.22 version
You may treat the call as closed and thanks for your prompt response
Probably a dup of ITS#6466. Closed, thanks. p.