Sqlplus script to check for row chaining

Here is the sqlplus scripting I use to check whether row chaining is degrading a query’s performance:

VARIABLE monitored_sid number;

begin

SELECT sid into :monitored_sid 
from v$session 
where audsid=USERENV('SESSIONID');

end;
/

select b.value "table fetch continued rows"
from
V$SESSTAT b
where b.SID = :monitored_sid
and b.STATISTIC# = (SELECT STATISTIC# FROM V$STATNAME 
WHERE NAME='table fetch continued row');

I create a test script with the problem query and put this code after it to see how much chaining affected it.

Here is an example of a fast query:

Elapsed: 00:00:15.87

table fetch continued rows
--------------------------
                     19723

Here is an example of a slow query:

Elapsed: 00:03:17.46

table fetch continued rows
--------------------------
                  23775056

This was the same query for two different date ranges.  The second range had a lot of row chaining and the query was much slower.

– Bobby

About Bobby

I live in Chandler, Arizona with my wife and three daughters. I work for US Foods, the second largest food distribution company in the United States. I have worked in the Information Technology field since 1989. I have a passion for Oracle database performance tuning because I enjoy challenging technical problems that require an understanding of computer science. I enjoy communicating with people about my work.

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