Method and apparatus providing optimistic locking of shared computer resources

A computer-readable medium carrying one or more sequences of instructions for updating a resource object, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

• receiving from a client process a request to update a particular resource object;
• sending to a lock manager process a request for a first lock for access to the particular resource object, the request including data indicating an optimistic lock type;
• receiving the first lock for access to the particular resource object, the first lock including data indicating the resource object, the optimistic lock type and a first value for a version number related to a number of changes to the resource object since the lock manager generated a lock data structure corresponding to the resource object;
• and
• updating the resource object by
• sending to a lock manager process a request for a second lock for access to the particular resource object, the request including data indicating the resource object identification and an exclusive lock type;
• receiving the second lock for access to the particular resource object, the second lock including data indicating the resource object identification, the exclusive lock type and a second value for the version number;
• determining whether the second value for the version number substantially equals the first value for the version number, and
• if the second value substantially equals the first value, then
• committing an updated resource object to the resource, and
• replacing the second value for the version number in the second lock with a third value for the version number, the third value computed by adding the second value and a predetermined version change value.

An apparatus for updating a resource object, comprising:

• a processor;
• one or more stored sequences of instructions which, when executed by the processor, cause the processor to carry out the steps of:
• receiving from a client process a request to update a particular resource object;
• sending to a lock manager process a request for a first lock for access to the particular resource object, the request including data indicating an optimistic lock type,
• receiving the first lock for access to the particular resource object, the first lock including data indicating the resource object, the optimistic lock type and a first value for a version number related to a number of changes to the resource object since the lock manager generated a lock data structure corresponding to the resource object;
• and
• updating the resource object by
• sending to a lock manager process a request for a second lock for access to the particular resource object, the request including data indicating the resource object identification and an exclusive lock type;
• receiving the second lock for access to the particular resource object, the second lock including data indicating the resource object identification, the exclusive lock type and a second value for the version number,
• determining whether the second value for the version number substantially equals the first value for the version number, and
• if the second value substantially equals the first value, then
• committing an updated resource object to the resource, and
• replacing the second value for the version number in the second lock with a third value for the version number, the third value computed by adding the second value and a predetermined version change value.

An apparatus for updating a resource object, comprising:

• a means for receiving from a client process a request to update a particular resource object;
• a means for sending to a lock manager process a request for a first lock for access to the particular resource object, the request including data indicating an optimistic lock type;
• a means for receiving the first lock for access to the particular resource object, the first lock including data indicating the resource object, the optimistic lock type and a first value for a version number related to a number of changes to the resource object since the lock manager generated a lock data structure corresponding to the resource object;
• and
• a means for updating the resource object, including
• a means for sending to a lock manager process a request for a second lock for access to the particular resource object, the request including data indicating the resource object identification and an exclusive lock type;
• a means for receiving the second lock for access to the particular resource object, the second lock including data indicating the resource object identification, the exclusive lock type and a second value for the version number;
• a means for determining whether the second value for the version number substantially equals the first value for the version number;
• a means for committing an updated resource object to the resource if the second value substantially equals the first value;
• and
• a means for replacing the second value for the version number in the second lock with a third value for the version number if the second value substantially equals the first value, the third value computed by adding the second value and a predetermined version change value.