How to tune when there is high I/O

Hi

My Awr shows there is I/O is High on few querys, how do i need to tune by database and the querys

Redologs are not in Raid 5   and the size of redolog is 100MB ( if i need to increase the size how do i need to find out what size  i need to increase)

   Physical              Reads              Elapsed
      Reads  Executions per Exec   %Total   Time (s)   %CPU    %IO    SQL Id
----------- ----------- ---------- ------ ---------- ------ ------ -------------
      4,945           2    2,472.5   12.7      676.0     .1   99.9 4abchk2bsb0tt
Module: SAPLSCCR
SELECT "TABNAME" , "TABCLASS" , "SQLTAB" , "CLIDEP" , "CONTFLAG" FROM "DD02L" WH
ERE "AS4LOCAL" = :A0 AND "TABCLASS" IN ( :A1 , :A2 , :A3 )