how to tail alert log in adrci

==> adrci

ADRCI: Release 11.2.0.3.0 - Production on Tue Jun 24 20:28:32 2014

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

ADR base = "/opt/app/oracle"
adrci>  show homes
ADR Homes:
diag/asm/+asm/+ASM
diag/asmtool/user_oracle/host_2740023319_80
diag/diagtool/user_oracle/host_2740023319_11
diag/tnslsnr/server/listener
diag/rdbms/dbname/DBNAME
diag/clients/user_oracle/host_2740023319_11
adrci> set homes diag/rdbms/dbname/DBNAME
adrci> show alert -tail -f
2014-06-24 12:08:41.139000 +00:00

sql for sizes

1. Top 10 segments

SELECT * FROM
(
select 
    SEGMENT_NAME, 
    SEGMENT_TYPE, 
    BYTES/1024/1024/1024 GB, 
    TABLESPACE_NAME 
from 
    dba_segments
order by 3 desc  
) WHERE
ROWNUM >= 10;