The following sections contain details about the effects of changes to a SYSTEM 2000
database definition on existing view descriptors.
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Changes that do not affect existing
view descriptors:
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creating or deleting indexes
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deleting schema items not referenced in any view descriptor
Note: If an access descriptor includes
the deleted schema item, users might create a view descriptor using
that item, which would cause a problem.
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inserting or deleting schema records in paths not referenced in any view descriptor
Note: If an access descriptor references
the changed path, users might create a view descriptor using that
path. This would cause a problem.
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Changes that might affect existing view descriptors:
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changing an item name. If the item name was used in a
where-clause or an
ordering-clause that is stored in the view descriptor, a
syntax error message appears when you try to use the view descriptor. The message indicates
an unrecognized
component name.
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changing the attributes of items that are not in the view descriptor but are referenced
in the stored where-clause.
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The following changes can cause existing view descriptors to fail:
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inserting or deleting a
level in the
path of a view descriptor.
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changing the attributes of an item or the
component number of an item, so that it points to something different. Specifically,
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You can change the pictures for
CHARACTER,
TEXT, and UNDEFINED item types, but you cannot change them to a
DATE or NUMERIC
item type.
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You cannot change a DATE item type to any other item type.
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changing the component number of parent records for any
schema item or record in the path of a view descriptor.
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deleting items that are referenced in a view descriptor.