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EXPDP And IMPDP Slow Performance In 11gR2 and 12cR1 And Waits On Streams AQ: Enqueue Blocked On Low Memory (Doc ID 1596645.1)

Last updated on OCTOBER 16, 2018

Applies to:

Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.

Symptoms

The import with DataPump of tables into an Oracle11g Release 11.2.0.4 database takes almost 45 minutes, while the same import into Oracle10g Release 10.2.0.4 only take 2 minutes.
The slow Import Data Pump performance problem might also reproduce in other Oracle11g Releases (like: 11.2.0.3) or Oracle12c Release 12.1.0.1.
The problem also reproduces when running an Export Data Pump job from such a release database.

The instance was started with following parameters (other configurations also possible):

 sga_target           = 5G
 shared_pool_size     = 0
 shared_pool_reserved_size = 48653926
 large_pool_size      = 0
 java_pool_size       = 0
 streams_pool_size    = 0
 compatible           = "11.2.0.4"
 pga_aggregate_target = 2G
 ...


An SQL trace file was created with:

ALTER SYSTEM SET events '10046 trace name context forever, level 12';

-- run import

ALTER SYSTEM SET events '10046 trace name context off';


The Data Pump Master and Worker trace file were analyzed with:

$ tkprof ORCL_dw00_11613.trc ORCL_dw00_11613_exe.out waits=y sort=exeela

showing:

...
Elapsed times include waiting on following events:
   Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  wait for unread message on broadcast channel
                                                415        1.00        404.95
  Streams AQ: enqueue blocked on low memory
                                                 12       60.00        720.10
  db file scattered read                          1        0.01          0.01
  Disk file operations I/O                       27        0.04          0.16
  direct path read                               12        0.00          0.01
  db file sequential read                        64        0.01          0.10
  control file sequential read                   35        0.00          0.04
  library cache: mutex X                          1        0.00          0.00
  direct path write                            1931        0.51         17.58
  KSV master wait                                 1        0.00          0.00

 
and:

$ tkprof ORCL_dm00_10978.trc ORCL_dm00_10978_exe.out waits=y sort=exeela

showing:

...
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  wait for unread message on broadcast channel
                                                698        1.00        684.41
  Disk file operations I/O                        2        0.00          0.00
  Streams AQ: enqueue blocked on low memory
                                                 21       60.00       1201.93
  db file sequential read                        28        0.00          0.03
  class slave wait                                1        0.00          0.00
  library cache: mutex X                          1        0.00          0.00
  direct path write                               2        0.00          0.00
  reliable message                               20        0.00          0.00
  db file scattered read                          1        0.00          0.00
  enq: RO - fast object reuse                     9        0.01          0.03
  enq: CR - block range reuse ckpt                9        0.00          0.05 


The tkprof output files clearly show that most time was waited on:

Streams AQ: enqueue blocked on low memory

 

Changes

 

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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