if the entire disk is corrupted and no backup is there don nothing sit and relax their is no possibility of recovery ...a backup is required for restoration and for recovery redo log and archive logs.
Once if you have theses than think of recovering ..a dba should always plan for the recovery scenario depending upon the criticality of the database.oracle provides 0% data loss facilty through data guard and online backup .its dba who has to decide.
If the user is complaining the hang problem ..then the experience of a dba reflects the work style that he is going to perform and basically as the rule suggest first try to connect to the database itself and fire some query to check whether you are allowed to connect or not if you are connected then check for any locked_objects by checking v$locked_object and dba_waiters and dba_blockers.then you have to eliminate the things which are working properly and targeting yourself to the weaker place and then check at os level that which process is consuming the most of the time and then analyze the problem if the problem relates to a single user process then check what that user is doing by checking the sql statement he is firing.than so on
after you get the legacy data thorugh exl format
1. you identify the which base table and which base column suitable for legacy data.
2.after that u have to use control file or dts processing to load the lagacy to eim table.
3. after that by using IFB file from eim to base table store the data.
The wildcard char % can be placed in one of three ways:
The searchwordhere% is the fastest because it can use an index if one is specified on that column. The other two %searchwordhere%, and %searchwordhere would never use the index even if one is specified and thus result in slow table scans.
You are running a cartisian query, typically by mistake. Make sure every table has a join criteria specified for it.
You are working on a table with 100+million rows.
The database server is busy doing a backup.
Check the disk IO for the process that appears hung and if the disk IO is increasing every 5-10 seconds then the job is not hung, it is just taking a while to complete.