| SAS/ACCESS Interface to SYSTEM 2000 Data Management Software: Reference |
As mentioned in ACCESS Procedure Reference,
changes to a database definition can affect descriptor files. Before changing
a definition, consider the following guidelines.
|
| Changes That Have No Effect on Existing View Descriptors |
The following changes to a SYSTEM 2000 database definition have no effect
on existing view descriptors:
- creating or deleting indexes.
- inserting new schema
items.
- deleting schema items not referenced in any view descriptor. (Note
that if an access descriptor includes the deleted item, users could eventually
create a view descriptor using that item, which would be a problem.)
- inserting or deleting schema records in paths not referenced in
any view descriptor. (Note that if an access descriptor references the changed
path, users could eventually create a view descriptor that would have a problem.)
|
| Changes That Might Have an Effect on Existing View Descriptors |
The following changes to a SYSTEM 2000 database definition might have
an effect on existing view descriptors:
- changing an item name. If the item name was used in a where-clause
or an ordering-clause stored in the view descriptor, you will receive a syntax
error message, indicating an unrecognized component name, when you try to
use the view descriptor.
- changing the attributes of items not in the view descriptor but
referenced in the stored where-clause.
|
| Changes That Cause Existing View Descriptors To Fail |
The following changes to a SYSTEM 2000 database definition cause existing
view descriptors to fail when they are used:
- inserting or deleting a level in the path of a view
descriptor.
- changing the attributes of an item or the component number of
an item, so that it points to something different. Specifically,
- You can change the pictures for CHARACTER, TEXT, and UNDEFINED
item types, but you cannot change them to a date or numeric item type.
- You cannot change a DATE item type to any other item
type.
- You cannot change a numeric item type to a non-numeric item type,
and you cannot change its picture.
- changing the component number of parent records for any schema
item or record in the path of a view descriptor.
- deleting items that are referenced in a view
descriptor.
The interface view engine validates the view against the current definition
and issues an informative error message if it detects discrepancies.
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
