Database connection script crashes after 4 successful connections - database

Question

I need to query a group of SAP sybase databases for some information and print that as a comma spearated list. So I figure I write a perl script that connects to any of those databases via DBI module. Here is what I came up with.
my $user = "someuser";
my $passwd = "somepassword";
my #sids=(filled with DB identifiers);
my $output="";
my $size;
my $version;
my $id;
my $dsn;
my $dbh;
my $sid;
my #row;
my $sth1;
my $sth2;
foreach $sid (#sids) {
print $sid."\n";
$dsn = "dbi:Sybase:server=$sid;charset=iso_1;tdsLevel=CS_TDS_50";
print $dsn."\n";
$dbh = DBI->connect($dsn, $user, $passwd,{ PrintError => 0,RaiseError => 0, AutoCommit => 1, syb_enable_utf8 => 1});
print "DBI OK\n" if defined ($dbh);
$sth1 = $dbh->prepare('select SUM(size) from master..sysusages WHERE dbid = 4 AND segmap = 3');
$sth2 = $dbh->prepare('select ##version');
$sth1->execute;
while (#row = $sth1->fetchrow) {
$size = $row[0];
}
$size = $size * 16 / 1024;
$sth1->finish;
$sth2->execute;
while (#row = $sth2->fetchrow) {
$version = $row[0];
}
$sth2->finish;
$output = $sid.",".$size.",".$version;
$dbh->disconnect;
print $output."\n";
}
When I execute this, it crashes after 4th iteration, because the connection handle is not set. So the connection of the fifth DB does not work anymore.
Can't call method "prepare" on an undefined value at ./check_sybasedbs.pl line 36.
Line 36 is the preparation of statement 1.
I tried putting sleep commands at various positions. I also tried to explicitly clean up the variables that are reused via undef. Now I am out of ideas and would really appreciate your input.

Answer 1

Your code could be written as sample below (please see if ... else ... block for $dbh)
use strict;
use warnings;
use feature 'say';
use DBI;
my($user, $passwd) = qw/someuser somepassword/;
my #sids = qw/server1 server2 ... server#/;
foreach my $sid (#sids) {
my $dsn = "dbi:Sybase:server=$sid;charset=iso_1;tdsLevel=CS_TDS_50";
say "DSN: $dsn";
my $dbh = DBI->connect($dsn, $user, $passwd, { PrintError => 1,
RaiseError => 1,
AutoCommit => 1,
syb_enable_utf8 => 1
}
);
if( not defined ($dbh) ) {
say "WARNING: Could not connect to $dsn";
} else {
say "INFO: DB connection established";
my($size,$version);
my $query = 'SELECT
SUM(size)
FROM
master..sysusages
WHERE
dbid = 4
AND
segmap = 3
';
my $sth = $dbh->prepare($query);
$sth->execute;
while (#row = $sth->fetchrow) {
$size = $row[0];
}
$sth->finish;
$query = 'select ##version';
$sth = $dbh->prepare($query);
$sth->execute;
while (#row = $sth->fetchrow) {
$version = $row[0];
}
$sth->finish;
$dbh->disconnect;
$size = $size * 16 / 1024;
say "SID: $sid, SIZE: $size, VERSION: $version";
}
}
NOTE: use strict; use warnings; helps to avoid many pitfalls, use diagnostics; helps to identify a problem in difficult cases
NOTE: $sth->fetchrow_hashref allows address hash element by name, no need to count index of array as in case $sth->fetch_rowarray

Answer 2

in my naiv thinking I hid some lines of code that I was convinced could not be the reason for this misbehaviour. As it turns out, it was. So the reason for my problem was a simple logical error, that caused the password, that was used after a connect to a certain DB to be wrong.