Change the huge table ( alter table ) with zero down time

Percona Toolskit is the best tool for the archiving this
1. steps for installing
wget http://www.percona.com/redir/downloads/percona-toolkit/2.1.1/percona-toolkit-2.1.1-1.noarch.rpm
2. rpm -ivh percona-toolkit-2.1.1-1.noarch.rpm
3 sometimes the dependencies for downloading are as follows:
wget http://www.percona.com/redir/downloads/percona-toolkit/2.1.1/percona-toolkit-2.1.1-1.noarch.rpm
wget ftp://mirror.switch.ch/pool/1/mirror/scientificlinux/5rolling/x86_64/SL/perl-TermReadKey-2.30-5.el5.x86_64.rpm
wget ftp://mirror.switch.ch/pool/2/mirror/fedora/linux/updates/15/x86_64/perl-DBD-MySQL-4.018-7.fc15.x86_64.rpm

NOTE: PARTITONS WILL NOT WORK IF WE HAVE FOREIGN KEY CONSTRAINTS
3. some of the examples are as follows
### just adding the column
pt-online-schema-change --alter="add column stat1 tinyint "  D=ledger,t=account_balance  --alter-foreign-keys-method='auto'--execute
### justing adding the two column and one column having foreign key
pt-online-schema-change --alter="add column operation_test4 varchar(50),add foreign key xyz4(operation_test4) references operation(type), add status5 varchar(10) default 'yes'"  D=wallet,t=transaction  --alter-foreign-keys-method='drop_swap' --execute
### Altering the ordinary table with partitions
pt-online-schema-change --alter="PARTITION BY RANGE (id) (PARTITION p0 VALUES LESS THAN (1000000),PARTITION p1 VALUES LESS THAN  (5000000),PARTITION p2 VALUES LESS THAN  (10000000),PARTITION p3 VALUES LESS THAN  (50000000),PARTITION p4 VALUES LESS THAN MAXVALUE)" D=wallet,t=transaction_test2 --execute
### this is for prompting password
pt-online-schema-change --alter="PARTITION BY RANGE (id) (PARTITION p0 VALUES LESS THAN (1000000),PARTITION p1 VALUES LESS THAN  (5000000),PARTITION p2 VALUES LESS THAN  (10000000),PARTITION p3 VALUES LESS THAN  (50000000),PARTITION p4 VALUES LESS THAN MAXVALUE)" -u kiran --ask-pass ,D=wallet,t=transaction_test2 --execute
### this is for hostname
pt-online-schema-change --alter="PARTITION BY RANGE (id) (PARTITION p0 VALUES LESS THAN (1000000),PARTITION p1 VALUES LESS THAN  (5000000),PARTITION p2 VALUES LESS THAN  (10000000),PARTITION p3 VALUES LESS THAN  (50000000),PARTITION p4 VALUES LESS THAN MAXVALUE)" -u kiran -h 10.10.8.141 --ask-pass ,D=wallet,t=transaction_test2 --execute
### this is for username and password
NOTE: PARTITONS WILL NOT WORK IF WE HAVE FOREIGN KEY CONSTRAINTS FOR THE TABLE
pt-online-schema-change --alter="PARTITION BY RANGE (id) (PARTITION p0 VALUES LESS THAN (1000000),PARTITION p1 VALUES LESS THAN  (5000000),PARTITION p2 VALUES LESS THAN  (10000000),PARTITION p3 VALUES LESS THAN  (50000000),PARTITION p4 VALUES LESS THAN MAXVALUE)" -u kiran -h 10.10.8.141 -p kiran@123 ,D=wallet,t=transaction_test2 --execute

The disadvanges of this tools is that if we have the trigger already then this tool does not work
The limitations are as follows:
pt-online-schema-change --alter="add column stat1 tinyint "  D=ledger,t=ppacounts_data  --alter-foreign-keys-method='auto'
The table `ledger`.`account_balance` has triggers.  This tool needs to create its own triggers, so the table cannot already have triggers.
[root@sniper kiran.chinta]#  pt-online-schema-change --alter="add column stat1 tinyint "  D=veles,t=ppacounts_data  --alter-foreign-keys-method='auto'
The table `veles`.`ppacounts_data` has triggers.  This tool needs to create its own triggers, so the table cannot already have triggers.
 pt-online-schema-change --alter="add column stat1 tinyint "  D=veles,t=transaction_log  --alter-foreign-keys-method='auto'
The table `veles`.`transaction_log` has triggers.  This tool needs to create its own triggers, so the table cannot already have triggers.

For more information about the tools
http://www.percona.com/doc/percona-toolkit/2.1/pt-online-schema-change.html