oracle log location

Release 11gR2
$ORACLE_HOME=/u01/app/oracle/product/11.2.0/grid_n
$ORACLE_BASE=/u01/app/oracle
$ORACLE_SID=tt

export HOST=`hostname -s`

ocssd
tail -f $ORACLE_HOME/log/$HOST/cssd/ocssd.log
tail -f  $ORACLE_HOME/log/$HOST/alert$HOST.log

ohasd
tail -f  $ORACLE_HOME/log/$HOST/ohasd/ohasd.log

oraagent

tail -f $ORACLE_HOME/log/$HOST/agent/ohasd/oraagent_oracle/oraagent_oracleOUT.log
tail -f $ORACLE_HOME/log/$HOST/agent/ohasd/oraagent_oracle/oraagent_oracle.log

cssdagent 
tail -f $ORACLE_HOME/log/$HOST/agent/ohasd/oracssdagent_oracle/oracssdagent_oracle.log

orarootagent

$ORACLE_HOME/log/$HOST/agent/ohasd/orarootagent_oracle/orarootagent_oracle.log

diskmon
$ORACLE_HOME/log/$HOST/diskmon/client.log

evmlogger 

tail -f $ORACLE_HOME/evm/log/$HOST_evmlogger.log

ALERT rdbms

tail -f $ORACLE_BASE/diag/rdbms/$ORACLE_SID/$ORACLE_SID/trace/alert_$ORACLE_SID.log

ALERT ASM 

tail -f $ORACLE_BASE/diag/asm/+asm/$ORACLE_SID/trace/alert_$ORACLE_SID.log