Creating a buffer point-in-time copy relationship for a point-in-time copy function executed to create a point-in-time copy relationship

A system, comprising:

• a plurality of storage volumes including a first, second, third, fourth and fifth volumes;
• and
• a storage volume controller connected to the volumes, the storage controller operated to perform:
• initiating a point-in-time copy function to create a new point-in-time copy relationship from a source volume comprising a first volume to a target volume comprising a second volume;
• detecting that the target volume of the new point-in-time copy relationship is a source volume of a first pre-existing point-in-time copy relationship having as a target volume the third volume;
• detecting that the target volume of the first pre-existing point-in-time copy relationship is a source volume of a second pre-existing point-in-time copy relationship having as a target volume the fourth volume;
• and
• creating a buffer point-in-time copy relationship having a source volume comprising the target volume of the first pre-existing relationship and a target volume comprising the fifth volume in response to detecting that the target volume of the new point-in-time copy relationship is the source volume of the first pre-existing point-in-time copy relationship and detecting that the target volume of the first pre-existing point-in-time copy relationship is the source volume of the second pre-existing point-in-time copy relationship, wherein the creating the buffer point-in-time copy results in a cascade of the first volume to the second volume, the second volume to the fifth volume, the fifth volume to the third volume, and the third volume to the fourth volume.

A computer program product on a computer readable storage medium for operating a point-in-time copy function with respect to a first volume, second volume, third volume, fourth volume, and fifth volume, the product comprising instructions executed to cause operations, the operations comprising:

• initiating a point-in-time copy function to create a new point-in-time copy relationship from a source volume comprising a first volume to a target volume comprising a second volume;
• detecting that the target volume of the new point-in-time copy relationship is a source volume of a first pre-existing point-in-time copy relationship having as a target volume the third volume;
• detecting that the target volume of the first pre-existing point-in-time copy relationship is a source volume of a second pre-existing point-in-time copy relationship having as a target volume the fourth volume;
• and
• creating a buffer point-in-time copy relationship having a source volume comprising the target volume of the first pre-existing relationship and a target volume comprising the fifth volume in response to detecting that the target volume of the new point-in-time copy relationship is the source volume of the first pre-existing point-in-time copy relationship and detecting that the target volume of the first pre-existing point-in-time copy relationship is the source volume of the second pre-existing point-in-time copy relationship, wherein the creating the buffer point-in-time copy results in a cascade of the first volume to the second volume, the second volume to the fifth volume, the fifth volume to the third volume, and the third volume to the fourth volume.