what max length an informix buttress increased?

i am perplexing emanate list following:

create list gtw_workflow_mon 
(
    workflow_name varchar(255) null, 
    workflow_loaded numeric(20) null, 
    activity_name varchar(255) null,
    flags integer null,
    monitor_name varchar(255) null,
    classname varchar(255) null,
    str0 varchar(255),
    str1 varchar(255),
    str2 varchar(255), 
    num0 varchar(255), 
    num1 varchar(255), 
    num2 varchar(255), 
    date0 varchar(255),
    date1 varchar(255), 
    date2 varchar(255), 
    primary pivotal (workflow_name, workflow_loaded, activity_name, monitor_name)
)

it fails due buttress length being infinite enough.