Patent ID: 7523204

Claim:
A process for quiescing a cluster of computer systems, wherein said cluster includes a master system and a plurality of subordinate systems that each may assume both an original state and a pending state that are either a quiesce state or an online state, the process comprising: (a) communicating from said master system to said plurality of subordinate systems a first message, wherein said first message requests that either said quiesce state or said online state be made said pending state; (b) preparing said plurality of subordinate systems to change from said original state to said pending state that was requested in said first message, wherein said preparing includes: (i) setting said pending state to be a partial state of the quiesce state; (ii) suspending input and output transactions with any client systems of said plurality of subordinate systems; (iii) flushing data for said transactions; and (iv) revoking data locks for and waiting for said client systems to flush logs; (c) determining in said plurality of subordinate systems whether said step (b) was successful; (d) sending vote messages from said plurality of subordinate systems to said master system, wherein each of the vote messages include a vote to either commit to or abort from changing from said original state to said pending state; (e) determining from said vote messages whether all of said plurality of subordinate systems have voted to commit; (f) communicating from said master system to said plurality of subordinate systems a second message, wherein said second message requests that said plurality of subordinate systems either commit or abort; (g) if said second message requests to commit, then: (i) if said pending state is said quiesce state, performing an operation in said plurality of subordinate systems; (ii) if said pending state is said online state, preparing said subordinate systems to resume said original state; and (iii) changing said plurality of subordinate systems from said original state to said pending state; and (h) if said second message requests to abort, then: (i) preparing said plurality of subordinate systems to remain in said original state; and (ii) resetting said pending state to said original state.