Increase import limit in vtiger

Under /modules/Import

$ImportConfig = array(
'importTypes' => array(
'csv' => array('reader' => 'Import_CSV_Reader', 'classpath' => 'modules/Import/readers/CSVReader.php'),
'vcf' => array('reader' => 'Import_VCard_Reader', 'classpath' => 'modules/Import/readers/VCardReader.php'),
'default' => array('reader' => 'Import_File_Reader', 'classpath' => 'modules/Import/readers/FileReader.php')
),

'userImportTablePrefix' => 'vtiger_import_',
// Individual batch limit - Specified number of records will be imported at one shot and the cycle will repeat till all records are imported
'importBatchLimit' => '2500',
// Threshold record limit for immediate import. If record count is more than this, then the import is scheduled through cron job
'immediateImportLimit' => '10000',

);

AND

vtiger -> Settings > Scheduler -> Scheduled Import -> Frequency 5 min from 15 min