Database management apparatus and recording medium with database management program recorded thereon

A database management apparatus comprising:

• a setting unit that receives a snapshot request requesting that a record in a database on a recording medium at a designated point in time be extracted and saved to another area, and records information indicating an extraction range of data to be extracted in the recording medium to a memory;
• an extraction unit that sequentially extracts records inside the extraction range, and records the extracted records to the other area;
• a monitoring unit that records information indicating an extraction-completed area with respect to which record extraction in the extraction range by the extraction unit has been completed and an extraction-remaining area with respect to which record extraction in the extraction range has yet to be performed to the memory on a timely basis;
• a subsequent update unit that judges, in a case where an instruction to update a record inside the extraction range by a subsequent transaction started after the designated point in time is received during the extraction process by the extraction unit, whether the record targeted by the update instruction is in the extraction-completed area or in the extraction-remaining area with reference to the memory, and, if the update target record is in the extraction-completed area, updates the update target record in the extraction-completed area, and, if the update target record is in the extraction-remaining area, records a map of the update target record in the extraction-remaining area to an area outside the extraction range and updates the map;
• and
• a restore unit that updates the update target record inside the extraction range to be the same as the map recorded and updated outside the extraction range, after the update target record inside the extraction range has been extracted by the extraction unit.

A database management method for being executed by a computer, the method comprising:

• a setting process of receiving a snapshot request requesting that a record in a database on a recording medium at a designated point in time be extracted and saved to another area, and recording information indicating an extraction range of data to be extracted in the recording medium to a memory;
• an extraction process of sequentially extracting records inside the extraction range, and recording the extracted records to the other area;
• a monitoring process of recording information indicating an extraction-completed area with respect to which record extraction in the extraction range in the extraction process has been completed and an extraction-remaining area with respect to which record extraction in the extraction range has yet to be performed to the memory on a timely basis;
• a subsequent update process of judging, in a case where an instruction to update a record inside the extraction range by a subsequent transaction started after the designated point in time is received during the extraction process, whether the record targeted by the update instruction is in the extraction-completed area or in the extraction-remaining area with reference to the memory, and, if the update target record is in the extraction-completed area, updating the update target record in the extraction-completed area, and, if the update target record is in the extraction-remaining area, recording a map of the update target record in the extraction-remaining area to an area outside the extraction range and updating the map;
• and
• a restore process of updating the update target record inside the extraction range to be the same as the map recorded and updated outside the extraction range, after the update target record inside the extraction range has been extracted in the extraction process.

A database management apparatus comprising:

• a processor to read an record in a snapshot range from a recording medium at a snapshot time point and save the record to another area,
• a memory to store data indicating the snapshot time point and the snapshot range,
• wherein the processor is arranged to record, to the memory, information indicating a read-complete area among the snapshot range and a read-remaining area among the snapshot range on a timely basis,
• to receive an instruction to update a target record inside the snapshot range,
• to compare a start point of a transaction of the instruction and the snapshot time point indicated by the data stored in the memory,
• to judge that the target record is in the read-complete area or in the read-remaining area, and
• to control the process of updating the target record according to the result of the comparing and the judging.