Another general principle is that PowerHA SystemMirror checks only what is being configured  at configuration time and not the whole configuration. PowerHA SystemMirror checks the  whole configuration at verification time. For example, when adding an HMC, you check only the new HMC (verify that it is pingable, at  an appropriate software level, and so on) and not  all  of the HMCs. Checking the whole  configuration can take some time and is done at verify and sync time rather than each  individual configuration step. Table 6-10 shows the general verification list. Table 6-11 shows the HMC communication verification list. General verification HMC communication verification Table 6-10 General verification list Table 6-11 HMC communication verification list Item Configuration  time Synchronization time Check that all RG active and standby nodes are on different  CECs, which enables the asynchronous mode of releasing  resources. Info Warning This code cannot run on an IBM POWER4 processor-based  system. Error Error Item Configuration  time Synchronization time Only one HMC is configured per node. None Warning Two HMCs are configured per node. None OK One node is without an HMC (if ROHA only). None Error Only one HMC per node can be pinged. Warning Warning Two HMCs per node can be pinged. OK OK One node has a non-pingable HMC. Warning Error Only one HMC with password-less SSH communication  exists per node. Warning Warning Two HMCs with password-less SSH communication exist per  node. OK OK One node exists with a non-SSH accessible HMC. Warning Error Check that all HMCs share the same level (the same version  of HMC). Warning Warning Check that all HMCs administer the CEC hosting the current  node. Configure two HMCs administering the CEC hosting  the current node. If not, PowerHA gives a warning message. Warning Warning Check whether the HMC level supports FSP Lock Queuing. Info Info 184  IBM PowerHA SystemMirror V7.2.3 for IBM AIX and V7.2.2 for Linux