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Oracle DBA Interview Questions

Q   |   QA

group by is used when we use aggregate functions on the columns in a query the other columns should be in group by query
example:
select empno,ename,sum(sal) from emp group by empno,ename
Order by is used to sort values either in ascending or descending order

Crosscheck command

DUPLICATE DATABASE

By running $ORACLE_HOME/rdbms/admin/spcreate.sql script

► Run a TOP command in Unix to see CPU usage (identify CPU killer processes)
► Run VMSTAT, SAR, and PRSTAT command to get more information on CPU and memory usage and possible blocking
► Run STATSPACK report to identify:
1. TOP 5 WAIT EVENTS
2. RESOURCE intensive SQL statements
► See if STATISTICS on affected tables needs to be re-generated
► IF poorly written statements are culprit, run a EXPLAIN PLAN on these statements and see whether new index or use of HINT brings the cost of SQL down.

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