Method, system, and program for establishing and using a point-in-time copy relationship

A method for establishing a point-in-time copy, comprising:

• generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship;
• initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• determining that data was written to one target storage area after establishing the point-in-time copy relationship;
• setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the data was written to the corresponding target area;
• receiving a request for data in the target storage area;
• if the indicator in the target relationship data structure for the requested target storage area is set to the first value, then returning the source storage area corresponding to the requested target storage area;
• and
• if the indicator in the target relationship data structure for the requested target storage area is set to the second value, then returning the requested target storage area from the target storage area.

A method for establishing a point-in-time copy, comprising:

• generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship, and wherein the storage areas comprise tracks;
• initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• determining whether a target track in a target cache was destaged to the target track after establishing the point-in-time copy relationship;
• and
• setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the target track was destaged from the target cache.

A system for establishing a point-in-time copy, comprising:

• means for generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship;
• means for initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• means for determining that data was written to one target storage area after establishing the point-in-time copy relationship;
• means for setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the data was written to the corresponding target area;
• means for receiving a request to update one source storage area included in the point-in-time copy relationship;
• means for determining whether the indicator in the target relationship data structure for the target storage area corresponding to the source storage area to update is set to the first value if the indicator in the source relationship data structure for the source storage area to update is the first value;
• means for writing the data in the source storage area to update to the target storage area if the determined indicator in the target relationship data structure is the first value;
• and
• means for applying the update to the source storage area after writing the data in the source storage area to the target storage area if the determined indicator in the target relationship data structure is the first value.

A system for establishing a point-in-time copy, comprising:

• means for generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship;
• means for initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• means for determining that data was written to one target storage area after establishing the point-in-time copy relationship;
• means for setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the data was written to the corresponding target area;
• means for receiving a request for data in the target storage area;
• means for returning the source storage area corresponding to the requested target storage area if the indicator in the target relationship data structure for the requested target storage area is set to the first value;
• and
• means for returning the requested target storage area from the target storage area if the indicator in the target relationship data structure for the requested target storage area is set to the second value.

A system for establishing a point-in-time copy, comprising:

• means for generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship, and wherein the storage areas comprise tracks;
• means for initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• means for determining whether a target track in a target cache was destaged to the target track after establishing the point-in-time copy relationship;
• and
• means for setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the target track was destaged from the target cache.

An article of manufacture for establishing a point-in-time copy, wherein the article of manufacture causes operations to be performed, the operations comprising:

• generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship;
• initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• determining that data was written to one target storage area after establishing the point-in-time copy relationship;
• setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the data was written to the corresponding target area;
• receiving a request to update one source storage area included in the point-in-time copy relationship;
• if the indicator in the source relationship data structure for the source storage area to update is the first value, then determining whether the indicator in the target relationship data structure for the target storage area corresponding to the source storage area to update is set to the first value;
• if the determined indicator in the target relationship data structure is the first value, then writing the data in the source storage area to update to the target storage area;
• and
• applying the update to the source storage area after writing the data in the source storage area to the target storage area if the determined indicator in the target relationship data structure is the first value.

An article of manufacture for establishing a point-in-time copy, wherein the article of manufacture causes operations to be performed, the operations comprising:

• generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship;
• initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• determining that data was written to one target storage area after establishing the point-in-time copy relationship;
• setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the data was written to the corresponding target area;
• receiving a request for data in the target storage area;
• if the indicator in the target relationship data structure for the requested target storage area is set to the first value, then returning the source storage area corresponding to the requested target storage area;
• and
• if the indicator in the target relationship data structure for the requested target storage area is set to the second value, then returning the requested target storage area from the target storage area.

An article manufacture for establishing a point-in-time copy, wherein the article of manufacture causes operations to be performed, the operations comprising:

• generating a source relationship data structure and target relationship data structure when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship, wherein the storage areas comprise tracks;
• initializing the source and target relationship data structures to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value;
• determining whether a target track in a target cache was destaged to the target track after establishing the point-in-time copy relationship;
• and
• setting the indicators to a second value in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area in response to determining that the target track was destaged from the target cache.