Sys columns defines what you see in the various tables within the application. While mainly interesting for developers, this can be adjusted as well by not very firm database users.
There is a max. limit of 30 columns per table – if you enter more values, you might see an error when opening the module with that table. To bypass this, you would need to change some code.
This simple table is split to the name of the listbox that holds the table, the source – most like a SQL query / view, the column name in the view that is the source for the column, a friendly column name that is shown to the end user, a sort-order in 100 steps – so you can mix in between and easily resort, a width setting and some extras like is this a datetime/numeric/boolean column so the sys search can configure itself right.
The first column (100) always defines the SelectTOP setting like ‘TOP 1000’ for the SQL query as well as the SelectORDER string (without ORDER BY) – in theory you could implement a GROUP BY after the ORDER BY definition through this column as well.
All this information is stored in the SQL database and will influence any open application session right away – assuming the specific form is opened – already open forms will not be affected in most cases.