General information

Review the following system behaviors regarding powering off:

• TC pairs are not affected when power is removed from a primary system while operations are in progress.

• When power is restored on the primary system, the system communicates with the secondary systems to confirm S-VOL pair status(es). Make sure that TC communications are fully restored (all paths have normal status) before beginning I/O operations to the P-VOL.

If the primary system accepts an I/O for a P-VOL when the path status is not normal, the primary system will split the pair. P-VOL status will change to PSUE(by RCU) but the primary system cannot change the pair status of the S-VOL.

• If power is removed from a secondary system or from a data path component while TC operations are in progress, the primary system detects the communication failure, splits all affected pairs, and generates SIMs reporting the failures. The primary system changes the P-VOL status to PSUE(by RCU) but cannot change the status of the S-VOLs.

• If a primary or secondary system is powered off and the backup batteries are fully discharged while pairs are split, differential data is retained to SSD. In this unlikely case, primary system copies differential data to secondary system when the pairs are resynchronized.