Since these are under "database relay" they only apply to requests via back-relay. Put them where they affect bdb: either global or under bdb.
Note that you need access rules both for access via DNs ending with relay's suffix and for DNs ending with bdb's suffix. I haven't checked which rules apply when, but the slapd-relay manpage talks about it.
I did these things that error solved.
moduleload /usr/lib/ldap/back_bdb.so database bdb suffix "dc=example,dc=com" rootdn "uid=demo,ou=people,dc=example,dc=com" password-hash {SSHA} directory /var/lib/ldap index objectClass eq
access to attrs="..........." (...................) cachesize 1500 sizelimit 1500
moduleload /usr/lib/ldap/back_relay.so database relay suffix "dc=play,dc=com relay "dc=example,dc=com" rootdn "uid=test,dc=example,dc=com" password-hash {SSHA}
access to attrs="............" (...................) sizelimit 1500
slapd is running perfectly. Now problem is that I want to add some entries in 'relay database'.
I tried to add some entries in relay database using this command. slapadd -b "dc=play,dc=com" -l ldap_relay.ldif -f /etc/ldap/slapd.conf
But, it's give me error. slapadd: database doesn't support necessary operations.