Good day, listers, I have two questions wrapped up in one issue. :) 1) What exactly is "enq: SI - contention" - it does not appear to be documented, and not many relevant hits on google 2) Why would a subpartition compress operation block simultaneous compress operations in different subpartitions or partitions? *Environment* Oracle 11.1.0.7.5 on Solaris 10 178 million row table with 15 partitions and 15 subpartitions each; non-uniform distribution of data *Explanation* Compress one subpartition in background: alter TABLE FGBTRND move subpartition FS04_P02 compress; Attempt to compress another subpartition at the same time: alter TABLE FGBTRND move subpartition FS04_P03 compress; A 10046 trace on the second will show wait events similar to the following: nam='enq: SI - contention' ela= 4951635 name|mode=1397293062 object #=44908 If I issue yet a third compress operation, I start seeing deadlock issues. All these events seem to be based on contention in the table itself (object_id = 44908 is table FGBTRND), not the sub/partitions. If there is a different trace event that would make this more clear/obvious, I am all ears. :) I tried looking through the list of trace events that I could set, and was unable to pinpoint one that might be helpful in this case. Any help would be much appreciated. Thanks much, -- Charles Schultz -- //www.freelists.org/webpage/oracle-l