The takeover mode for the unavailable cluster remains in place until another mode is selected or the unavailable cluster is restored. Only one available cluster must enable the takeover mode because all peers share the enablement after it is enabled. 

GLYPH<SM590000> Write Ownership Takeover (WOT) 

When WOT is enabled for an unavailable cluster, ownership of a volume is taken from the unavailable TS7700 Cluster when the volume is accessed. Full access is allowed through the requesting TS7700 Cluster in the grid and all other available TS7700 clusters in the grid. 

The mode for the unavailable cluster remains in place until another mode is selected or the failed cluster is restored. If volumes were taken over with the read-only takeover mode, enabling write ownership takeover allows any previous takeovers and future takeovers to enable updates. 

Scratch mounts continue to prefer volumes that are owned by the available clusters. Only after all available candidates are exhausted does it take over a scratch volume from the unavailable cluster. 

You can set the level of ownership takeover, Read-only or Write, through the TS7700 MI or LI REQ. 

More than one cluster can have ownership takeover enabled. For example, if two clusters both become unavailable, ownership takeover must be enabled against both clusters individually so that the remaining cluster or clusters can access volumes that are owned by the two unavailable clusters. 

Important:  You cannot change the takeover mode of a cluster in service. 

For more information about an automatic takeover, see 2.4.33, “Autonomic Ownership Takeover Manager” on page 92. 

## 2.4.4 I/O TVC selection 

All vNodes in a grid feature direct access to all logical volumes in the grid. The cluster that is selected for the mount is not necessarily the cluster that is chosen for I/O TVC selection. All I/O operations that are associated with the virtual tape drive are routed to and from its vNode to the I/O TVC. 

When a TVC that is different from the local TVC at the actual mount point is chosen, this mount is called a remote mount. The TVC is then accessed by the grid network. Selecting the TVC can be influenced by using several methods. 

During the logical volume mount process, the best TVC for your requirements is selected based on the following considerations: 

GLYPH<SM590000> Availability of the cluster 

GLYPH<SM590000> Copy Consistency policies and settings 

GLYPH<SM590000> Scratch allocation assistance (SAA) for scratch mount processing 

GLYPH<SM590000> DAA for specific mounts 

GLYPH<SM590000> Override settings 

GLYPH<SM590000> Cluster family definitions 

GLYPH<SM590000> Disk cache residency and recall times 

GLYPH<SM590000> Network latency times 

