Load balancing

Hello, I set up a wide ip in a GTM with 2 pools as members. and with the following irule definition. In order for this irule to work what should be the load balancing method to use;

when DNS_REQUEST { if { [matchregion ldns "BXB-IDMS-DNS"]} { if { [active_members pl_bxb-idcmysql-read_3306] > 0} { pool pl_bxb-idcmysql-read_3306

    }
    else {
        pool pl_chi-idcmysql-read_3306
        log local0. "No Active members in MYSQL for BXB so use CHI MYSQL by DNS [IP::client_addr]"
    } 
}
elseif { not [matchregion ldns "BXB-IDMS-DNS"] } {
    if {  [active_members pl_chi-idcmysql-read_3306] > 0 } {
            pool pl_chi-idcmysql-read_3306

    }
    else {
     pool pl_bxb-idcmysql-read_3306
     log local0.  "No Active members in CHI MYSQL for CHI so use BXB MYSQL by DNS [IP::client_addr]" 
    }
 }

}

Thanks for any help,