Informix database backups 
Author Message
 Informix database backups

Quote:

>In X-Informix-List-Id: <news.1091>  Don Amby asks:
>> I am relatively new to Informix, and am wondering if it is possible to do
>> non-interactive backups of an Informix database?  I can do this for my normal
>> backups, via cron, and I want to be able to do the same for backing up a
>> database.

>Depending on which version of Informix you are using, your best bet would
>be to use DBEXPORT.  This will create a schema for rebuilding your database as
>well as unloading all of your tables into delimted ASCII.  It also has the
>advantage of being able to write directly to tape.

There are three ways to do Informix backup: "tbtape", "tbunload" and
"dbexport". Each with different performance( time and storage required) and
dbexport is the WORST one in terms of time required !

1. tbtape command allows you to do on-line backup of the whole database
   installation ( Yes, that's right; You can't just backup a single database
   or table).
   The advantages of using tbtape command are:

   * On-line backup and databases are not locked. A must for commerical
     environment.
   * Incremental backup (level 0, 1 and 2) saves time and storage space.
   * Output tapes can be used with logical log backups in recovery process
     to bring database installation back to the content just before the
     database corrupted.
   * Fast. It unload data in binary in multiple disk page units with
     minimal processing.

   Disadvantages:

   * Not fast enough :-) Reading data off the disk and writing to tape all
     in single thread I/O. For a commerical MP environment with large
     database installation( 10 - 50 GB), it's unacceptable !

2. tbunload/tbload commands allow you to do online backup of a specific
   database of table.
   The advantages:

   * On-line backup.
   * Fast. It also unload data in binary in multiple disk page units with
     minimal processing.

   The disadvantages:
   * No incremental backup.
   * Can't be used with log backup tapes in recovery process to bring
     database to the most recent date.
   * Database/table target is locked during unloading.

3. dbexport/dbimport: they are not really designed for doing database
   backup IMO. They are used to dump database in ASCII format for
   further processing or exporting to other RDBMS. The performance is
   very bad due to extensive processing.

  Now, as for doing non-interactive backup; I don't see how you can do it
  with any of the above. They all interactively prompt you things like
  "Please mount the tape and press return to continue ...". Tbtape command
  also prompt for level of backup intended( Why can't they implement this as
  a command line option ?!?). That's the only minor thing keep you from
  doing unattended (cron job like) backup.

  I mean, you have to change tapes, don't you ? If your database is small
  and can be stored on one tape, as some other net people pointed
  out, you can port the "tcl" and "expect" utilities to  take care of the
  very first prompt. Good Luck.

  If you have any good strategy or experience in backup/recover Informix
  database, I would lke to know and please send me an email !

Eric Chen

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Sat, 15 Oct 1994 04:43:37 GMT
 Informix database backups


Quote:
(Eric Chen) writes:

+---------------
|    The advantages of using tbtape command are:
|
|    * On-line backup and databases are not locked. A must for commerical
|      environment.
+---------------
Not exactly.  The database gets locked if the archive doesn't fit on
a single reel.  The lock exists during the time the tape is rewinding
and the operator is mounting a new reel.  This can be several minutes,
and is completely unacceptable.

We had to solve this problem for our commercial customers.  Our approach
was to create a named pipe (/dev/tape) and point Informix at it in the
tbconfig file.  We lied to Informix about the size of the tape device
(99999999...) and then wrote our own set of programs to read the pipe
and write the tape.  Our programs can toggle drives on systems that
have more than one, and buffer to disk during the time the tape is
not available.

--

Anasazi, Inc. - 7500 North Dreamy Draw Drive, Suite 120, Phoenix, Az 85020
(602) 870-3330            "I read the news today, oh boy!"  -- John Lennon



Sun, 16 Oct 1994 13:20:48 GMT
 Informix database backups

Quote:


>(Eric Chen) writes:
>+---------------
>|    The advantages of using tbtape command are:
>|
>|    * On-line backup and databases are not locked. A must for commerical
>|      environment.
>+---------------
>Not exactly.  The database gets locked if the archive doesn't fit on
>a single reel.  The lock exists during the time the tape is rewinding
>and the operator is mounting a new reel.  This can be several minutes,
>and is completely unacceptable.

  I agree with you.

Quote:
>We had to solve this problem for our commercial customers.  Our approach
>was to create a named pipe (/dev/tape) and point Informix at it in the
>tbconfig file.  We lied to Informix about the size of the tape device
>(99999999...) and then wrote our own set of programs to read the pipe
>and write the tape.  Our programs can toggle drives on systems that
>have more than one, and buffer to disk during the time the tape is
>not available.

  If the tape device is designed like RAID to provide "concate/stripe
virtual tape" by spreading output to several(configurable) tape device in
transparent way, then it will eliminate not only the problem you
mentioned above but also tape channel performance bottleneck !
  Does this product exist? Yes !!

  But how about the other performance bottleneck -- the single thread
I/O as done by tbtape to read data off the disk is still there. Did you
guys provide any solution on that for customers ? The typical speed of
reading database off disk is probably 600 - 800 KB/s which means 20 hours
to do 50GB database and I doubt the "commercial customers" still care the
few minutes locking between changing tape reels :-)

  Your response is welcomed.

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Mon, 17 Oct 1994 11:16:23 GMT
 
 [ 3 post ] 

 Relevant Pages 

1. Remote Informix Database Backup

2. Unattended Informix database backups?

3. Informix Database Backups

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