Crash recovery

The Compound Document framework provides for the possibility of system and Workspace crashes while in the midst of operations on a document.

After a document is first opened and its data is streamed in, the command log records all the commands (and their arguments) together with the commands' selections that operate on the document's data. This matched pair of selection and command is called a command binding.

The document passes the command binding to the command log. The command log contains all the command bindings that have been executed since the document was last committed to storage.

Deleting the command log

The command log is deleted whenever the entire persistent state of the document component is committed to storage.

Recovering from a crash

When a document crashes and later restarts, it uses the command log to bring the document into the same state that it was just before it crashed. Every command is executed on a matched selection. The only command that is not executed is the one that was being executed at the time of the crash.


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