Data within a file system might not be in the appropriate format to be accessed if moved between different types of systems. For example, files stored in proprietary binary formats often require conversion for use on the target platform. Files containing databases might not be in a standard format that allows their access when moving a file system between various systems, even if those systems use the same byte order. Oracle 10g's Cross-Platform Transportable Tablespace is a notable exception; if used, this feature provides a consistent format across many platforms.
Some data is inherently portable, such as plain ASCII files. Other data is designed to be portable and the applications that access such data are able to access it irrespective of the system on which it was created, such as Adobe PDF files.
Note that the CDS facilities do not convert the end user data. The data is uninterpreted by the file system. Only individual applications have knowledge of the data formats, and thus those applications and end users must deal with this issue. This issue is not CDS-specific, but is true whenever data is moved between different types of systems.
Even though a user might have a file system with data that cannot be readily interpreted or manipulated on a different type of system, there still are reasons for moving such data by using CDS mechanisms. For example, if the desire is to bring a file system off line from its primary use location for purposes of backing it up without placing that load on the server or because the system on which it will be backed up is the one that has the tape devices directly attached to it, then using CDS to move the file system is appropriate.
An example is a principal file server that has various file systems being served by it over the network. If a second file server system with a different operating system was purchased to reduce the load on the original server, CDS can migrate the file system instead of having to move the data to different physical storage over the network, even if the data could not be interpreted or used by either the original or new file server. This is a scenario that often occurs when the data is only accessible or understood by software running on PCs and the file server is UNIX or Linux-based.