Example of rolling out schema changes in a grid

You can roll out schema changes to replicated tables through a grid without shutting down your applications.

Suppose that you have a grid replicate set named gridset that contains 12 replicates, each of which represents a different table. You want to alter the data types of columns in five tables. The grid contains four servers.

To roll out schema changes without application downtime:

Change any connections from the original application to the replication server named cdr1 to connect to the replication server named cdr2.

On the cdr1 server, connect to the stores_demo database, connect to the grid, and alter the five tables:

dbaccess stores_demo -
EXECUTE PROCEDURE ifx_grid_connect('grid1', 'gridset', 4);
SET LOCK MODE TO WAIT 120;
ALTER TABLE customer ADD prefix (char15);
ALTER TABLE items MODIFY order_num (bigint);
ALTER TABLE stock MODIFY description (lvarchar);
ALTER TABLE cust_calls ADD call_descr2 (lvarchar);
ALTER TABLE manufact MODIFY manu_name (char32);

The ifx_grid_connect() procedure changes the tables on cdr1 but delays the propagation of the changes to the other replication servers.

Update the application to reflect the new schema for the five tables and connect to the server cdr1.
Close the connections from the original application.
On the server cdr1, propagate schema changes to the other replication servers by running the following statement:
```
EXECUTE FUNCTION ifx_grid_release('grid1', 'gridset');
```
On the server cdr1, create a derived replicate set named alterSet that contains the altered tables by running the following command:
```
cdr define replicateset --needRemaster=gridset alterSet
```
From the server cdr1, remaster the altered tables on all replication servers by running the following command:
```
cdr remaster replicateset --master=cdr1 alterSet
```
From the server cdr1, synchronize the data on all replication servers by running the following command:
```
cdr check replicateset --replset=alterSet --repair --master=cdr1 --all
```
On the server cdr1, drop the derived replicate set by running the following command:
```
cdr delete replicateset alterSet
```