SAS/SHARE User's Guide

Backward and Forward Compatibility

Forward and Backward Compatibility in a Cross-Release Environment shows a client/server computing environment that contains a Version 7 server.

Note: Because Version 7 and Version 8 features are virtually identical, references to Version 7 in the figure also apply to Version 8. [cautionend]
The server contains both Version 6 data and Version 7 or Version 8 data that is accessed by a Version 6 client and a Version 7 or Version 8 client.

Forward and Backward Compatibility in a Cross-Release Environment

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[1] A Version 6 client can read, write, and update a Version 6 data file.

[2] A Version 7 or Version 8 client can read, write, and update a Version 7 or Version 8 data file.

[3] A Version 6 client can read, write, and update a Version 7 or Version 8 data file that has not implemented Version 7 or Version 8 features such as long variable names. In this instance, a Version 6 client and its application are forward compatible with a Version 7 or Version 8 server and its data because the data does not contain Version 7 or Version 8 features. However, a Version 6 client and application are not forward compatible with a Version 7 or Version 8 server and data that does include Version 7 or Version 8 features.

[4] A Version 7 or Version 8 client can read, write, and update a Version 6 data file as long as the application does not implement Version 7 or Version 8 features such as long variable names. In this instance, a Version 7 or Version 8 client and application are backward compatible with Version 6 data if the application does not exploit Version 7 or Version 8 features. If the program does exploit Version 7 or Version 8 features, the program's attempt to open a Version 6 data set fails.

Note: You can access Version 6 and Version 7 or Version 8 data in a mixed-mode library if you intentionally update or write the data in the correct format. See Mixing Cross-Version Data Files in a Single Library for more information about accessing data files in a mixed-mode library. [cautionend]

Backward and forward compatibility allows cross-version access in a restricted mode. This means that Version 6 clients can operate on Version 7 or Version 8 data that does not contain Version 7 or Version 8 features, and Version 7 or Version 8 applications that do not exploit Version 7 or Version 8 features can operate on Version 6 data.

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