An error occurred while updating disk io failure


Here are few interview questions with answers found on the internet.As I don't have time to format these questions to wiki I am just posting them hoping someone to format them. Explain the difference between a hot backup and a cold backup and the benefits associated with each.ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. Candidate should mention use of DECLARE statement, a function must return a value while a procedure doesn't have to. What is a mutating table error and how can you get around it? It occurs because the trigger is trying to update a row it is currently using.NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time. Where in the Oracle directory tree structure are audit traces placed? The usual fix involves either use of views or temporary tables so the database is selecting from one while updating the other. Describe the use of %ROWTYPE and %TYPE in PL/SQL Expected answer: %ROWTYPE allows you to associate a variable with an entire table row.NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly. The %TYPE associates a variable with a single column type. What packages (if any) has Oracle provided for use by developers?



You should also look at the logic involved in the application getting the error message. If they can mention a few of these and describe how they used them, even better.Expected answer: SQLCODE returns the value of the error number for the last error encountered. The tkprof tool is a tuning tool used to determine cpu and execution times for SQL statements.The SQLERRM returns the actual error message for the last error encountered. Expected Answer: There are 12 types of triggers in PL/SQL that consist of combinations of the BEFORE, AFTER, ROW, TABLE, INSERT, UPDATE, DELETE and ALL key words: BEFORE ALL ROW INSERT AFTER ALL ROW INSERT BEFORE INSERT AFTER INSERT etc. You use it by first setting timed_statistics to true in the initialization file and then turning on tracing for either the entire database via the sql_trace parameter or for the session using the ALTER SESSION command. This indicates you need to tune the sort area parameters in the initialization files. What parameters control copy latches When you get excessive contention for the copy latches as shown by the "redo copy" latch hit ratio. What happens if the constraint name is left out of a constraint clause The Oracle system will use the default name of SYS_Cxxxx where xxxx is a system generated number. How can this be prevented or mitigated This is caused by large or long running transactions that have either wrapped onto their own rollback space or have had another transaction write on part of their rollback space.If they include the SQL routines provided by Oracle, great, but not really what was asked. Describe the use of PL/SQL tables Expected answer: PL/SQL tables are scalar arrays that can be referenced by a binary integer. However if you also have chained rows this can hurt performance. How do you set up tablespaces during an Oracle installation?