Oracle执行计划的IN-OUT字段含义

The In-Out Column  其代表执行步骤的 串行与并行输入输出情况

SERIAL (blank): Serial execution. Currently, SQL is not loaded in the OTHER column for this case.
SERIAL_FROM_REMOTE (S -> R): Serial execution at a remote site.
PARALLEL_FROM_SERIAL (S -> P): Serial execution. Output of step is partitioned or broadcast to parallel execution servers.
PARALLEL_TO_SERIAL (P -> S): Parallel execution. Output of step is returned to serial QC process.
PARALLEL_TO_PARALLEL (P -> P): Parallel execution. Output of step is repartitioned to second set of parallel execution servers.
PARALLEL_COMBINED_WITH_PARENT (PWP): Parallel execution; Output of step goes to next step in same parallel process. No interprocess communication to parent.
PARALLEL_COMBINED_WITH_CHILD (PWC): Parallel execution. Input of step comes from prior step in same parallel process. No interprocess communication from child.
https://docs.oracle.com/database/121/TGSQL/tgsql_interp.htm#TGSQL94734