Troubleshooting query performance

Question

one of the queries that used to take 2 minutes, is taking more than an hour in last few weeks. I am trying to figure out what might be causing. There have been no changes to the query. I am looking for some help on how to troubleshoot.
The following is my query
SELECT Node,NodeAlias,MailStop,Customer,Summary,DeviceType,Tally,Severity,
TO_CHAR(FirstOccurrence, 'YYYY-MM-DD HH24:MI:SS' ),TO_CHAR(LastOccurrence,'YYYY-MM-DD HH24:MI:SS' ),SiteID,ServerSerial,ProblemID,TroubleTicket
From REPORTER_STATUS 
WHERE
(ElementMgmt = 4) and (NodeAlias = 'xxx') and LastOccurrence > TRUNC(SYSDATE - 7) ORDER BY LastOccurrence descI ran a explain plan on this query and this is what it's showing. It's showing a cost of 868990 on the select statement. Not sure where to go from here. Tables are partitioned by quarter.
  ID OPERATION           OPTIONS  OBJECT_NAME     OBJECT_ALIAS          QBLOCK_NAME POSITION
   0 SELECT STATEMENT    NULL     NULL            NULL                  NULL          868990
   1   SORT              ORDER BY NULL            NULL                  SEL$1              1
   2     PARTITION RANGE ALL      NULL            NULL                  NULL               1
   3       TABLE ACCESS  FULL     REPORTER_STATUS REPORTER_STATUS@SEL$1 SEL$1              1Edited by: rmalghan145 on Dec 19, 2011 7:53 AM

Answer 1

rmalghan145 wrote:
one of the queries that used to take 2 minutes, is taking more than an hour in last few weeks. I am trying to figure out what might be causing. There have been no changes to the query. I am looking for some help on how to troubleshoot.Has this table changed in any way in the last couple of weeks? Has a lot of data been added to it? Are the statistics up to date?
Please read the following thread and provide the information mentioned in it: {message:id=9360003}