Change log indicator

Hi,

I have turned on "Log data changes" indicator for a Z table. The changes to the table gets logged when I update it through SM30 but not when I do it through my Z program that does a direct update using the "Update" , "Delete" statements. Is there any other setting that I need to do? I am not doing any lock/unlock in the Z program. Could this be the reason?

Regards,

Hari.