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DB migration

in General Discussion

Hi,

I have a DB migration activity scheduled this week.

I am using datapump to perform this activity.

Could you please suggest what are the prechecks need to be done from my side.

Below are the source and target details.

Source --

OS -- Red Hat Enterprise Linux Server release 6.10 (Santiago)

DB -- 12.1.0.2.0

DB size -- 126MB

This is standalone DB.

This is QA env

Target --

OS -- Red Hat Enterprise Linux Server release 7.9 (Maipo)

DB -- 19.0.0.0.0

DB size -- 8MB

This is standalone DB.

This is QA env

Regards,

Balaji

10 answers0 replies

10 Comments

Balaji

Aug 31

•

Hi Piyush,

Thank you for your clarifications.

thomasjack6000

Aug 31

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Piyush Ranjan

Aug 30, 2022

•

For Exact database size, use below mentioned query.

select
"Reserved_Space(GB)", "Reserved_Space(GB)" - "Free_Space(GB)" "Used_Space(GB)",
"Free_Space(GB)"
from(
select 
(select sum(bytes/(1014*1024*1024)) from dba_data_files) "Reserved_Space(GB)",
(select sum(bytes/(1024*1024*1024)) from dba_free_space) "Free_Space(GB)"
from dual
);

For more queries related to database size, visit the link mentioned below:

https://www.support.dbagenesis.com/post/check-oracle-database-size

Balaji Mohan

Aug 31, 2022

Replying to

Thank you for clarification and queries.

Piyush Ranjan

Aug 30, 2022

•

Hi Balaji,

When using the datapump approach, there isn't much to verify before exporting the data; simply make sure you have enough space for the dumpfile and that the character sets are the same on both databases to reduce the chance of problems.

For more data pump details. Click on the below link to know more: https://www.support.dbagenesis.com/post/oracle-data-pump-expdp-impdp

Piyush Ranjan

Aug 30, 2022

•

Replying to

You state in your query that the size of the source database is 126M. If it is 126 GB, take into account having twice as much space as the database size which is 252 GB aprox.

Balaji Mohan

Aug 30, 2022

Replying to

Hi Piyush,

Thank you . I am sorry for the confusion.

The below select query shows 126 mb as DB size

select sum(bytes)/1024/1024/1024 size_in_GB from dba_data_files;

and other below select query shows 126GB.

col "Database Size" format a20

col "Free space" format a20

col "Used space" format a20

select round(sum(used.bytes) / 1024 / 1024 / 1024 ) || ' GB' "Database Size"

, round(sum(used.bytes) / 1024 / 1024 / 1024 ) -

round(free.p / 1024 / 1024 / 1024) || ' GB' "Used space"

, round(free.p / 1024 / 1024 / 1024) || ' GB' "Free space"

from (select bytes

from v$datafile

union all

select bytes

from v$tempfile

union all

select bytes

from v$log) used

, (select sum(bytes) as p

from dba_free_space) free

group by free.p

Could you please verify query to check for DB size.

Balaji Mohan

Aug 31, 2022

Replying to

Hi Piyush,

As per estimation size of dumpfile , it is 79.70 GB."

expdp ESTIMATE_ONLY=YES full=y NOLOGFILE=YES

If it is 126 GB, take into account having twice as much space as the database size which is 252 GB aprox.

Should I consider twice as much space as the DB size or twice as much space as the dumpfile size for space required for import on target . Could you please explain.

Regards,

Balaji