初学Abaqus，请大声帮忙回答一个简单问题

Solver problem. Zero pivot when processing D.O.F. 3 of 2 nodes.
The nodes have been identified in node set
WarnNodeSolvProbZeroPiv_3_1_1_1_1
最后面的数字_3_1_1_1_1分别代表什么含义？