DFSMS Message ARC1237I - No Space for Migration Copy

This morning I was trying to SMP/E RECEIVE a bunch of PTFs as part of a DB2 tool maintenance. After receiving 20 PTFs, the job went down with a storage space abend IEC032I E37-04 on the SMPPTS dataset.

I noticed that the SMPPTS dataset already had 16 extents. I tried to add some cylinders, but I couldn't. So I tried to change the SMS volume by HMIGRATEing and HRECALLing the dataset. But the HMIG command failed with this message:

ARC1001I hlq.SMPPTS MIGRATE FAILED, RC=0037, REAS=0000
ARC1237I NO SPACE FOR MIGRATION COPY    

I tried migrating the dataset directly to Level 2 by issuing this command:

HMIG / ML2

When I issued this command, it failed with the message:

ARC1001I hlq.SMPPTS MIGRATE FAILED, RC=0080, REAS=0000
ARC1280I MIGRATION FAILED - DATA SET IS IN NEED OF BACKUP

I issued this command to take a DFSMS backup:

HBACKDS

After the backup was complete, I tried to migrated to L2, it worked !!

After the migrate was complete, I recalled the dataset. It went to a different volume with more space and also had only 1 extent filled.