Database Handling Failed Scenario - Joomla! Forum - community, help and support

hi everyone, new joomla , ask following question.

1. connection , disconnection
i use following execute query database:

code: select all

$db =& jfactory::getdbo();
$db->setquery( $queryvar );
$result = $db->loadresult();

from understanding database object created , connection establised, happen after finish executing loadresult.
q1: connection database automatically terminate after loadresult() finish executing or have make function terminate it?
q2: $db object destroy @ point?

2. failed scenario
i using innodb engine. friend recommended using try/catch/finally. including code structure below:

code: select all

try
{
   begintransaction()
   //database action here      
   commit()
}
catch error
{
   rollback()  //cancel saving database, , rollback changes
}
finally
{
   closeconnection()
   //set database handle null close connection
}

q3. has implement scenario in joomla , correct approach?
q4. joomla have similar handle situation failed transaction?

i appreciate advice can give. website building, expecting high traffic 5000-10000 users. definite proper db management prioritize achieve. have checked documentation jdatabase::committrans() , there nothing implement function.

thank everyone.