ATTACH commands were hung and useless

Question

Version:11.2.0.2
Platform :Linux 5.6
I mistakenly started an impdp job by setting PARALLEL = 4 with a single dumpfile. From OTN i've found that PARALLEL > 1 is only usefull if you have multiple files so that each slave process can work on each dumpfile.
This single dumpfile size was only 300mb.
Since the impdp was hung at 99% percent for 2 hours. I attached to the job using
impdp username/password ATTACH=<job_name>In the status output, I saw
Current Parallelism: 4I wanted to reduce this to 1. So, I did this
Import> PARALLEL = 1But the above command was hung. So, I started another Putty session , attached to this job and checked the status. The Parallelism was still 4. I tried the same step (setting PARALLEL = 1) two more times. Both were hung again.
Eventually I decided to kill the job. So, I did this
Import> KILL_JOBAnswered 'yes' for the prompt. This was hung as well. Later I had to kill this impdp using good old kill -9 .
Has anyone succesfully decreased PARALLELISM by attaching to the job ?
Commands executed ( PARALLEL =1 and KILL_JOB) after attaching were hung. Is it because this is Linux ?

Answer 1

First, running parallel with a value greater than the number of dump files for import is ok. Not really ideal, but not bad like export.
My guess on the hang is that the job was really done and the process rundown hung for some reason, that is why your change of parallelism didn't take effect. You really could not communicate to the data pump process. Changing parallelism does work, but it waits for a convenient time to reduce the work load and since your workload was essentially done, it never changed.
Dean