IDS Forum

Re: How to Restore Level 1 backup after level 0

Posted By: Martin Furderer
Date: Friday, 16 February 2018, at 8:53 a.m.

In Response To: How to Restore Level 1 backup after level 0 (MUNAWAR AHMED)

Hi,

see Mike Walker's answer.

A little bit of (simplified) background:

Backup is divided into backup of dbspaces and backup of logical logs.

The backup of dbspaces can be of level 0, 1 or 2.

The backup of logical logs is recommended but not strictly necessary.

In a similar way, the restore is divided into two parts: physical restore

and logical restore.

You need to start a restore with the physical restore of a level 0 backup.

This copies the data in the level 0 backup to disk. After this you can

restore a level 1 (or a level 2) backup. Once this is done, the data is on

disk, but it's state is not logically consistent. This is because at the time

of the backup there may have been some open transaction(s). Therefore

the logical part of the restore is necessary. At a minimum this needs to check

whether there were open transactions ... and roll them back. However,

there is the option to first restore logical logs that have been backed up

after the level 0, 1 or 2 backup of dbaspaces was done. This way it is not

only possible to restore the system just to the point when the last level

0, 1 or 2 backup of dbspaces was done. Provided logical logs were backed up

afterwards (i.e. as they were filled by ongoing transactions), these logical

logs can be restored. Their log records (of those ongoing transactions) can

be rolled forward. Once there are no more logical logs to restore, the same

thing needs to happen to finish the restore: check whether there are open

transactions and roll them back. With that the system then is logically

consistent and can be used again.

The "catch" with this system is: all physical restore parts (level 0, 1 and 2)

must be done before the system starts to treat logical log records, either to

roll forward log records from restored logical logs, or just to rollback open

transactions (without restore of logical logs). Once the system starts with

the logical log record part (even if there is nothing to do because there were

no open transactions at the time of the backup) ... it is no longer possible

to do a physical restore of any level 1 or 2 backup.

That's why in manual operation "ontape" asks for any level 1 (or level 2)

restore before it starts looking at logical log records. Any level 1 (or level 2)

backup must be restored at this point.

Regards, Martin

--
Martin Fuerderer
Informix Development Germany

e-mail: martin.furderer@hcl.com

HCL Technologies Germany GmbH
Frankfurter Ring 17
80807 Munich, Germany
http://www.hcltech.com/de

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________________________________
From: ids-bounces@iiug.org <ids-bounces@iiug.org> on behalf of MUNAWAR AHMED <mahmed04@i2cinc.com>
Sent: Friday, February 16, 2018 13:43
To: ids@iiug.org
Subject: How to Restore Level 1 backup after level 0 [40693]

Hi,
let assume, today is Friday and i have level zero backup of Monday and level 1
backup of Wednesday.
Now i restored Level 0 backup on an instance via ontape -r, it was done
successfully.Now i also want to restore level 1 backup.

How is it possible? to restore level 1 backup after successful completion of
level 0.

Thanks.

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Messages In This Thread

• How to Restore Level 1 backup after level 0
  MUNAWAR AHMED -- Friday, 16 February 2018, at 7:43 a.m.
  • RE: How to Restore Level 1 backup after level 0
    Mike Walker -- Friday, 16 February 2018, at 8:22 a.m.
  • Re: How to Restore Level 1 backup after level 0
    MUNAWAR AHMED -- Friday, 16 February 2018, at 8:33 a.m.
    • RE: How to Restore Level 1 backup after level 0
      Mike Walker -- Friday, 16 February 2018, at 8:51 a.m.
  • Re: How to Restore Level 1 backup after level 0
    Martin Furderer -- Friday, 16 February 2018, at 8:53 a.m.

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