pegasus/src/Pegasus/Repository/FileBasedStore.cpp - diff

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version 1.7, 2008/09/17 18:35:56

version 1.8, 2008/10/24 17:48:53

Line 427

// InstanceTransactionHandler

// This class is used to manage a repository instance transaction. The

// This class uses a simple recovery scheme to avoid corruption of the

// transaction is started when the class is instantiated, committed when

// instance repository during a "write" operation. A transaction is

// the complete() method is called, and rolled back if the destructor is

// started when the class is instantiated, committed when the complete()

// called without a prior call to complete().

// method is called, and rolled back if the destructor is called without

// a prior call to complete().

// The appropriate repository write locks must be owned while an

// InstanceTransactionHandler instance exists.

// This algorithm is used to allow recovery on an operation failure:

// 1. Check to see if any rollback files exist for instances of the

// given class. If so, perform rollback

// 2. Create a rollback file for the instance file. The rollback file

// contains the original size of the instance file.

// 3. Create a rollback file for the index file. The rollback file is a

// copy of the instance file.

// 4. Update the instance file to perform the operation.

// 5. Update the index file to perform the operation.

// 6. Increment the free count in the index file if necessary, and

// perform reorganization if the limit is reached.

// 7. Delete the rollback files.

// The recoverability algorithm itself works as follows:

// 1. Delete the index file.

// 2. Rename the index rollback file to have the same name as the

// index file.

// 3. Truncate the instance file to have the same number of bytes as

// indicated in the instance rollback file.

// 4. Delete the rollback files.

////////////////////////////////////////////////////////////////////////////////

class InstanceTransactionHandler

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