flyingfb wrote:

>
> sometimes, we need change the metadata, for example, change
> type of a column from Integer to varchar, we thought we must
> backup and restore, is it right?

You can make many data type changes by altering a field to a
larger type in the same "group" - e.g. smallint to int or
double and strings to larger strings.

Changing between "groups" - integers to strings, for example -
requires something more elaborate. Backup/restore won't do it,
because the backup includes the data definitions.


The usual procedure is to add a new temporary field of the
type you want to the table, copy the data to the new field,
drop the old field and rename the new field to the old name.
That gets complicated when the table is referenced in views,
procedures, etc. If you're facing a major set of schema
changes, look at the tools available here

http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_contrib_download


Good luck,

Ann