PARALLEL_MIN_SERVERS Does Not Limit The Number Of Parallel Processes At Startup in 12c (Doc ID 1678111.1)

Last updated on MARCH 15, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.1 to 12.1.0.1 [Release 12.1]
Oracle Database - Enterprise Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
Information in this document applies to any platform.

Symptoms

 Setting the value of parallel_min_servers in 12c to a value lower than the default causes this parameter to be ignored:

 

Default value of PARALLEL_MIN_SERVERS in DB is 4*2*2 = 16
------------------------------------------------------------
SQL>  show parameter PARALLEL_MIN_SERVERS
 
NAME                                 TYPE          VALUE
------------------------------------ ------------- ---------
parallel_min_servers                 integer       16
 
 
 
 
Number of parallel processes is 16
------------------------------------------------------------
[oracle@cdcjp81vm6 ~]$ ps -ef|grep ora_p0
oracle    3028     1  0 15:16 ?        00:00:00 ora_p000_db12c
......
oracle    3086     1  0 15:16 ?        00:00:00 ora_p00f_db12c
 
16 rows.
 
 
Modified PARALLEL_MIN_SERVERS  to 8, and restart database.
------------------------------------------------------------
SQL> alter system set PARALLEL_MIN_SERVERS = 8;
 
System altered.
 
SQL> shutdown immediate
......
SQL> startup
ORACLE instance started.
Database opened.
 
 
 
PARALLEL_MIN_SERVERS was changed to 8, but the number of parallel processes 
was 16 as before.
------------------------------------------------------------
SQL> show parameter PARALLEL_MIN_SERVERS
 
NAME                                 TYPE       VALUE
------------------------------------ ---------- ---------
parallel_min_servers                 integer    16
SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 
64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing 
options
[oracle@cdcjp81vm6 ~]$ ps -ef|grep ora_p0
oracle    4002     1  0 15:28 ?        00:00:00 ora_p000_db12c
......
oracle    4056     1  0 15:28 ?        00:00:00 ora_p00f_db12c
 
16 rows.

Changes

 The same setting was working with 11g Release 2 but no longer does in 12c.

Cause

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