Help: can't add columns

Hello, I am a new user to Informix. We are running informix on a UNIX server. Right now, I can't add column to my table, I got error -162. I used command 'tbcheck -cr' to check the system, I have following massage: Validating INFORMIX-Online reserved pages validating PAGE_PZERO... validating PAGE_CONFIG... validating PAGE_1CKPT & PAGE_2CKPT... using check point page PAGE_2CKPT Validating physical log pages... Validating logical logs... Validating PAGE_1DBSP & PAGE_2DBSP... using dbspace page PAGE_1DBSP Validating PAGE_1PCHUNK & PAGE_2PCHUNK... using primary chunk page PAGE_2PCHUNK Validating PAGE_1ARCH & PAGE_2ARCH... using archive page PAGE_1ARCH Could someone tell me what those message means... Thanks, Tia.