By Ray Olson
When you save a file by giving it the name of another existing file, this does not mean that the new file is identical to the original one. As a matter of fact, in CATIA, a file is identified by its name but also by its UUID (Universally Unique Identifier) which differs from one file to another (except when a file is a copy of another one, for instance).
To illustrate this, let's suppose we have an CATProduct named Product-ALL containing two CATParts, named Part-A.CATPart and Part-B.CATPart:
Product-ALL and the two parts it points to are saved using File > Save As,
then the Product-ALL is closed. A new part is created using File > New.
The new part is saved as "Part-B" in the same folder and replacing the file, then Part-B is closed.
When re-opening Product-ALL, you are informed that Part-B cannot be found.
The reason is that the new document saved as "Part-B" has been given a new UUID when using File > New and this new UUID is different from the one assigned to the original Part-B. Therefore, the link between Product-ALL and Part-B is considered as broken, even if there is a Part-B.CATPart document, because the original Part-B does not exist anymore.
If you want to reroute the link to the new Part-B.CATPart, you need to select Edit > Links then click Replace to fix the link of file name and UUID.
When saving an existing file in another directory without changing the file name (which means that you have now two files), note that you can open only one of these files at a time. If one of them is already open, you cannot open the other and will see the message below:
The reason is that both files have the same UUID (Universally Unique Identifier).
To avoid this, each file must have its own UUID.
This can be done by selecting File > New from.
Also, in the Save As dialog box, specify the location of the document to be saved as well as its name and type.
The Save as new document check box lets you save an existing document under a new name but with a new UUID (Universally Unique Identifier).
This option is effective only when the document is saved in its native format, i.e. when the document type (displayed in the Save as type box) has not been modified. Otherwise, this option is ineffective.
Note that when using File > Save As for a new document, the Save as new document checkbox is not displayed in the Save As dialog box because it is irrelevant in this context.
The UUID (Universally Unique Identifier) and file name is also used to link CATIA Drafting Views to CATIA CATProducts and CATParts files.
From Wikipedia:
A universally unique identifier (UUID) is a 128-bit number used to identify information in computer systems. The term globally unique identifier (GUID) is also used. When generated according to the standard methods, UUIDs are for practical purposes unique, without depending for their uniqueness on a central registration authority or coordination between the parties generating them, unlike most other numbering schemes. While the probability that a UUID will be duplicated is not zero, it is close enough to zero to be negligible.
