Liferay custom table refreshed on building service

[deepak...@gmail.com]

Hi , I am using liferay 6.1 with Oracle 10 have requirements to increase custom table colomn size from default 75 to 400 varchar. But table gets refreshed each time when building service and all the data lost and set default size 75 .
Note- not using ext please suggest solution without ext.

Thanks
Deepak

[deepak...@gmail.com]