Distributed caching scheme for database systems

A data management method servicing mobile customers, wherein data of a customer is stored in a central database and in at most one of a plurality of spatially distributed local databases, comprising the steps of:

• querying a local database proximate to the customer for the customer's data,
• when the customer's data is not found in the proximate local database, retrieving the customer's data and a pointer associated with the customer's data from the central database,
• determining whether the pointer identifies a second local database other than the proximate local database as containing the customer's data,
• when the pointer does not identify a second local database, writing the data in the proximate local database.

A data management method servicing mobile customers, wherein data of a customer is stored in a central database and in at most one of a plurality of local databases, comprising the steps of:

• querying a first local database proximate to the customer for the customer's data,
• when the customer's data is not found in the first local database, retrieving the customer's data and a pointer associated with the customer's data from the central database,
• determining whether the pointer identifies a second local database as containing the customer's data,
• when the pointer identifies the second local database, commanding the second local database to destroy its copy of the customer's data, and
• after the second local database destroys its copy of the customer's data, writing the customer's data in the first local database.

A data management method servicing mobile customers, wherein data of a customer is stored in a central database and in at most one of a plurality of local databases, comprising the steps of:

• querying a first local database proximate to the customer for the customer's data,
• when the customer's data is not found in the first local database, retrieving a first copy of the customer's data and a pointer associated with the customer's data from the central database,
• determining whether the pointer identifies a second local database as containing a second copy of the customer's data,
• when the pointer identifies a second local database, retrieving the second copy from the second local database,
• commanding the second local database to destroy its copy of the customer's data,
• determining whether the second copy is different from the first copy, and
• when the copies are different, writing the second copy to the central database and to the first local database.

A database caching method for use at one of a plurality of regional databases, comprising:

• receiving a query for a data record,
• determining if the requested data record is present at the one regional database,
• if not, querying a central database for the data record,
• receiving, in response to the central database query, a copy of the data record and a pointer referring to another regional database,
• transmitting a command to the other regional database to destroy its copy of the data record, and
• upon receipt of a message indicating that the other regional database has destroyed its copy of the data record, storing a copy of the data record at the one regional database.

A database caching method for use at one of a plurality of regional databases, comprising:

• receiving a query for a data record,
• determining if the requested data record is present at the one regional database,
• if not, querying a central database identifying the data record,
• receiving, in response to the central database query, a pointer referring to another regional database,
• querying the other regional database for the data record,
• receiving the data record from the other regional database, and
• storing a copy of the data record at the one regional database,
• wherein the act of receiving the data record from the other regional database signifies that the other regional database has destroyed its copy of the data record.

A database caching method for use at a central database, comprising:

• receiving a query from a first regional database for a data record,
• providing to the first regional database a copy of the requested data record and a pointer identifying another regional database that may store a copy of the data record,
• receiving from the first regional database a confirmation that a copy of the data record has been stored at the first regional database, and
• altering a stored copy of the pointer to identify the first regional database.

A database caching method for use at a central database, comprising:

• receiving a query from a first regional database for a data record,
• retrieving a pointer associated with the data record,
• if the pointer identifies a second regional database that is different than the first regional database, signaling the second regional database to destroy its copy of the data record,
• upon receipt of a confirmation from the second regional database signifying that it has destroyed its copy of the data record, providing a copy of the data record to the first regional database.