Is that a behavior of DBI or DBD::Oracle?
My script says prepare or die, so any retries would have had to come directly
from the DBD::Oracle module
Script basically says:
use DBD::Oracle;
my $dbh = DBI->connect("dbi:Oracle:$dbSID", $user, $passwd, {AutoCommit => 0 });
my $statement = <<END;
20 line select statement
END
my $arraySelect = $dbh->prepare($statement) or die $!;
$arraySelect->execute();
while ( my ($var1, $var2, $var3, $var4) = $arraySelect->fetchrow_array() ) {
<perl code to process row of data which includes a couple of “if next”
statement blocks with no reference to arraySelect inside the while loop>
}
$arraySelect->finish();
$dbh->disconnect();
I don’t work much with the DBD::Oracle module or perl and what I have is just
reworked from scripts others have written.
Is there parameters for the DBD::Oracle functions that can affect their
behavior? If this is behavior of the execute function, I really need to be able
to reign it in to limit its impact if it ever does it again. Not knowing why
the issue triggered in the 1st place, I don’t know how to reproduce it to test
if any mitigations are sufficient.
Cheers,
John
From: Geoffrey Rommel <[email protected]>
Sent: Thursday, 13 February 2020 2:56 AM
To: JohnD Blackburn <[email protected]>
Cc: [email protected]
Subject: Re: Perl script excessively executing statement
CAUTION: This email originated from outside of the organization. Do not click
links or open attachments unless you recognize the sender and know the content
is safe.
I don't work with Oracle, but here's a guess. Maybe the database was
unresponsive before your script started running, not as a result of it. If so,
maybe your script tried to prepare the statement, failed, and retried 12000
times. Eventually the DBA noticed the problem and restarted the database, at
which time your script was terminated along with everything else.
On Tue, Feb 11, 2020 at 11:56 PM JohnD Blackburn
<[email protected]<mailto:[email protected]>> wrote:
Hi all,
I have a perl script in my monitoring system that has been working for months
without an issue.
Basically, it connects to an Oracle 12c database, prepares a statement, then it
executes the statement, then it has a while loop to process the returned rows.
So under normal conditions the statement is executed once every 5 minutes.
Now on Friday last week, it did something really strange which I cannot account
for the behaviour.
According to the DBA, the statement in the script was executed 12610 times over
a 50 minute period causing the database to become non-responsive. The DBAs
also stated that the script only connected to the database once at the
beginning of the 50 minute period. Average execution time of the statement was
0.26 seconds.
According to the log for my script, the script only executed once at the
beginning of the 50 minute period, and then after that, returned to executing
every 5 minutes.
Since that incident, the statememt in question has only executed the expected
12 times per hour.
I have yet to find a satisfactory reason the SQL statement from this perl
script executed so many times in the 50 minute period.
Script is running on an Oracle Linux 7.7 server with;
* oracle 12c client installed
* perl 5.16.3
* perl-DBI 1.627-4 ( from Oracle Linix Latest yum repository)
* perl-DBD-ODBC 1.50.-3 (from EPEL)
* DBD::Oracle 1.80 (from CPAN)
Oracle 12 database is on a remote server.
Anyone have any ideas why the SQL statement would have been executed 12000+
times in a 50minute period, when the script and its schedule should not have
executed the SQL any more frequiently than 12 times an hour?
Regards,
John
