With lock migration, if the EX mode is specified in another transaction branch after lock has been specified in PR mode, all the subsequent lock is in EX mode. In a global transaction, once resources are put under lock in EX mode, the resource cannot be put under lock in PR mode. All resources are under lock in EX mode.

If resources are under lock with lock migration specified, they are automatically released when the global transaction terminates. If the resources can be released before the termination of the global transaction, take the following procedures:

• Releasing resources with the function dc_lck_release_byname()
  To release a resource from lock with lock migration specified before commit/rollback processing is executed, specify the resource name, and call the function dc_lck_release_byname() (which releases resources from lock). The resource can be released from lock in any transaction branch. In this case, the resource cannot be released until the function dc_lck_release_byname() is called as many times as the lock count specified for the resource in the global transaction.
  
• Releasing resources with the function dc_lck_release_all()
  If the function dc_lck_release_all() (which releases all resources from lock) is called to a transaction branch, all the resources are released no matter how many times lock has been specified in any transaction.
  

Do not access a resource for which lock has been specified (access to an already allocated resource or a new lock request) in the following case:

• After lock migration occurred with the function dc_rpc_call() of a synchronous-response-type RPC, the function dc_rpc_call() returned with an error (e.g., timeout).
  Operation is not ensured if access is made to the resource.
  

The figure below shows lock migration.

Figure 4-23 Outline of lock migration