Method for the dynamic replication of data under distributed system control to control utilization of resources in a multiprocessing, distributed data base system

A method for operating a computing apparatus including a plurality of nodes, with each node having means for storing at least one data item and means responsive to a request for accessing a specified data item, and communication means interconnecting selected nodes, the computing apparatus being operated in response to a request for accessing a specified data item and controlling the modification of copies of the data item at a plurality of nodes, the method characterized by the steps of:

• generating a data request specifying a required currency for a specific data item at the node of the request;
• determining if the node of the request views any other node as having for said specific data item a currency status which is in conflict with said required currency;
• resolving currency conflicts;
• and thereafter
• granting the request for accessing the specified data item.

A method for operating a first node of a multinode computing apparatus, said first node including means for storing at least one data item, means responsive to a request for accessing a specified data item, and a port for communicating data and control signals with respect to at least one other node, said first node being operated in response to a request for accessing a specified data item and controlling the modification of copies of data items at said first node, the method characterized by the steps of:

• generating a data request specifying a required currency for a specific data item at said first node;
• determining if said first node views any other node as having for said specific data item a currency status which is in conflict with said required currency;
• communicating a message containing a data request to other nodes and receiving from each such other node a response resolving any currency conflicts;
• and thereafter
• granting the request for access to the specified data item.

A method for operating a first node of a computing system, said first node including means for storing at least one data item, means responsive to a request for accessing a specified data item, and a port for communicating data and control signals with respect to at least one other node, said first node being operated in response to the request for accessing the specified data item and controlling the modification of copies of data items at said first node, the method characterized by the steps of:

• storing or enabling generation of a set of dipole halves at said first node, with a dipole half for each other node with which said node shares a data item;
• responsive to a request quark specifying for a given data item the dipole half desired at said first node by a related node and the dipole half at the related node for said first node, executing a quark processing unit comprising the following steps:
• determining if any dipole halves stored at said first node for said given data item have a conflicting status;
• generating a conflict quark for each dipole half having a conflicting status for communication to the other node having the conflicting status;
• waiting for a response to each communicated conflict quark;
• modifying dipole halves stored at said first node for other nodes as required to reflect processing of said request quark, and modifying the dipole half at said first node for said related node as required to reflect processing of said request quark;
• and
• selectively generating a response quark or otherwise responding to the originator of said request quark.

A method for operating a computing system including a plurality of nodes interconnected by a communication network;

• each node storing in a data file a plurality of data items which may be unique or copies of data items stored at other nodes;
• each node, responsive to a request for access to a specified data item by an application, controlling the applications's access to said stored data item;
• and each node selectively communicating the updated data item to other nodes storing copies of the specified dta item;
• wherein improvements to the controlling, storing, and communicating steps provide dynamic replication of data under distributed system control and comprise the steps of:
• storing a dipole with respect to a data item shared by a node pair, a dipole half being stored in each node of the node pair specifying the status, assumed by this node, of the shared data item at a related node, with the data state of a given data item at this node being defined by the set of dipole halves stored at this node with respect to all related nodes sharing copies of that given data item;
• responsive to a request for access to a data item from an application at this node having a copy of the data item at a data state consistent with the request, granting the request without network interaction with related nodes;
• responsive to a request for access to a data item from an application at this node having a data state conflict with the request, negotiating a dipole change with each related node with which this node receiving the access request shares a conflicting dipole, and upon resolution of all such conflicts, granting the request;
• and
• responsive to an update request which has been granted, storing the updated data item at this node and only thereafter in connection with an application request communicating from some other node, or in the course of data base conformation processing, communicating the updated item to that other node.