Import of Partitioned tables running for Long time

Hi,

Recently we did full import of our Database from 10g to 11g. There are couple issues found during import.
1) The export activity took around 3 hrs to complete but Import took around 20hrs to complete.
2) Database size has grown large than it is expected.

I tried to debug the issue and find the solution and below are the details.

 

Issue1:

Tablespaces with partitioned objects have grown from 20GB to 100GB.

This is issue is due to new hidden parameter _partition_large_extents introduced in 11gR2 specifically.

 

Solution:

Before start of import set the parameter _partition_large_extents to FALSE

 

Issue2:

Import during TUP1:

  full import of 10g database is done into 11g database as part of platform migration. This activity took around 20 hrs to complete.

Identified Time consuming tasks:

1)    We have partitoined table with around 4000+ partitions – 10 hrs – Due to large number of partitions and many partitions have data in them.

2)      Table Statistics import – 6 hrs

3)      Index statistics - 2 hr

 

Solution:

To minimize the downtime, the full database import is split and performed. Below is the complete set of activities tested with timing details captured. This total activity has brought down the total time to 4 hrs.

 1) Import Full database Import of full database excluding some objects & statistics.
Excluded partition tab;e and objects statistics
  e.g.: Impdp full=y exclude=TABLE:<TABLE NAME>
2) Imp excluded objects into a different table Import excluded Partitioned object sepeartely with merge partition option
 A separate table is created without any partitions using partitions=merge and remap_table options.
 
  e.g.: impdp TABLES=<TABLE_NAME> REMAP_TABLE= SOURCENAME:TARGETNAME 

3) Import Metadata Only Import of metadata only for excluded object into database
Imported only metadata only of excluded source table along with partitions
  e.g.: impdp CONTENT=METADATA_ONLY 

4) Insert data  Insert data from table created in step 2 to Table created in Step 3 using sqlplus
#Import data from non partitioned table to partitioned table

#5) Gather stats Gather statistics of all objects
This is estimated time and needs to be tested again.