Only using 1 parallel DML thread when using INSERT with APPEND ENABLE_PARALLEL_DML PARALLEL(8)

Inserting into a table (interval partitioned) in parallel and enabling parallel DML -- does not write in parallel the first time, but does every successive time unless destination table is recreated.

Create destination table:

create table metrics_out

(

"_TIMESTAMP_EXTRACT_KEY" NUMBER(*,0),

RECORD_ID NUMBER(18,0),

LINE NUMBER(38,0),

. . .

)

PARTITION BY RANGE ("_TIMESTAMP_EXTRACT_KEY") INTERVAL (1)

(PARTITION "SYS_P9999"  VALUES LESS THAN (4) SEGMENT CREATION IMMEDIATE) ;

INSERT into destination table with parallel DML enabled:

insert /*+ enable_parallel_dml append parallel(8) monitor */

   into metrics_out

   select 6,

    RECORD_ID,

    LINE,

. . .

from stage.metrics;

Only using 1 parallel writer, of course very slow.

After deleting all rows in destination table or truncating it, then doing an INSERT again, it's