Latch Free wait event

Hi,
Some times I see the "latch free" wait event as top when there is slowness in the system.  Please help what could be the problem ?

SQL Texts for that latch free are:

1.
/* OracleOEM */
    select *
    from (select /*+ use_nl (v$sql) */   sql_text, hash_value,
    sharable_mem, persistent_mem,                           
    runtime_mem, sorts,                           
    loaded_versions,open_versions,                           
    users_opening, executions,                           
    users_executing, loads,                           
    invalidations,parse_calls,                           
    disk_reads,buffer_gets,                           
    rows_processed,optimizer_mode,                           
    parsing_user_id,parsing_schema_id,                          
    kept_versions, address,                            module,  
                            action,                           
    serializable_aborts,                           
    (1-(greatest(disk_reads,0)/greatest(buffer_gets,1)))*100,   
            greatest(buffer_gets,0)/decode(greatest(executions,0),
    0,-1,executions),             greatest(buffer_gets,0)/