Abstract: A data writing device capable of dynamically switching between a write-through mode and a write-behind mode for writing transaction data into a disk including: a memory with a queue management table for managing a write disk queue and a write memory queue to store the transaction data; means for registering the write memory queue in the table when load exceeds a predetermined threshold value, and for deleting the write memory queue in the table when the load is below the predetermined threshold value; means for receiving the transaction data stored in the write disk queue, and writing the received transaction data into the disk; and means for receiving the transaction data stored in the write disk queue, and writing the received transaction data into a redundant memory.

Abstract: A method, apparatus and computer product wherein means and mechanisms are provided whereby, in a distributed or clustered shared file system, (1) concurrency classes may be defined specifying granularity of locking, whether locks are cached, and whether modified data is written-through at the completion of updates, (2) certain files, file types, or files and/or file types as used by given applications or classes of applications, may be associated with concurrency classes, and (3) for each usage of a file by an application, the associated concurrency class determines a policy for choosing specific concurrency and coherency control mechanisms to be used for accessing the given file.

Abstract: The invention includes a proxy server that constitutes means for providing, verifying and logging a digital signature for a message that is to be exchanged via a network, so that a security function for a digital signature can be implemented without changing an application program. In an example embodiment, a digital signature system comprises: applications for performing data processing; and a signature server connected to the applications via a LAN, wherein the signature server intercepts the message communication from the application to a destination device outside the LAN, provides a digital signature for a message document to be exchanged through communication, and transmits the obtained message document to the destination device.