OAM does not select full volumes to satisfy a write request. You might choose to eject full volumes from a library (for example, using ISMF to obtain a list of all full volumes in a library, then using the EJECT line operator) to streamline processing.
Thus, it is important to select a threshold value that allows the volumes to be marked full in a consistent manner. You must consider the size of the objects stored into the group. If the size of the objects is consistent, choose a threshold that is slightly larger than that size. The VOLUME FULL THRESHOLD is set on a storage group basis. When the number of available kilobytes on a volume falls below the VOLUME FULL THRESHOLD for the storage group to which that volume belongs, the volume is marked full and will not be used for any later write requests. If you find that volumes are not being selected for new objects and they are not being marked full, increase the value for this parameter.
Additionally, during OAM initialization, a volume previously set to FULL=Y with the MODIFY OAM,UPDATE command might be subsequently marked not full. This is because the volume's current tape-full percentage is less than the value of the TAPEPERCENTFULL parameter on the SETOAM statement. If you intend to mark the volumes in an Object or Object Backup storage group unavailable as candidates for write requests, you could mark them as WRITABLE=N because the writable status of the volume does not change during OAM initialization.