Description: Because of release enhancements and service, the size of the z/OS root file system (or "version root file system") continues to grow from release to release. The size of the z/OS root file system, whether HFS or zFS, is expected to closely approach, if not exceed, the limit of 3339 cylinders on a 3390-3 device.
It is advisable to have the z/OS root file system within a single data set for ease of management.
| Element or feature: | Multiple. |
| When change was introduced: | General migration action not tied to a specific release. |
| Applies to migration from: | z/OS V1R13 and z/OS V1R12. |
| Timing: | Before installing z/OS V2R1. |
| Is the migration action required? | No, but recommended for ease of management if your z/OS root file system resides on a 3390-3 volume (or another DASD volume that is close to the 3390-3 limit of 3339 cylinders). |
| Target system hardware requirements: | None. |
| Target system software requirements: | None. |
| Other system (coexistence or fallback) requirements: | None. |
| Restrictions: | None. |
| System impacts: | None. |
| Related IBM® Health Checker for z/OS® check: | Use IBM Health Checker for z/OS check CHECK(IBMUSS, ZOSMIGREC_ROOT_FS_SIZE) to determine if a volume has enough space for the z/OS root file system. |
If your z/OS root data set cannot fit on the volume or volumes you have defined for it, divide the z/OS root, with the smaller file systems being managed together.
Remember that all systems to which you deploy the z/OS root file system need sufficient DASD space to hold the z/OS root.
Reference information: For more information about multivolume data sets, see z/OS DFSMS Implementing System-Managed Storage.