Taking longer than expected (Nov 13, 2014)

Message boards : Technical News : Taking longer than expected (Nov 13, 2014)

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Eric KorpelaProject Donor
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Message 1600681 - Posted: 13 Nov 2014, 17:14:27 UTC

The Astropulse database fix is taking longer than expected. By one measure (the amount of data written into the new database spaces) we're 70% done. By another measure (the number of table rows showing up in the table stats) we are 25% done. This is after 5 days. I'm inclined to believe the 25% number, in which case we will run out of SETI@home work before Astropulse is back online. If you don't have a low share back-up project, now might be time to add one.

Informix never ceases to astonish me with the way it does things. The table rebuild is neither maxing out CPUs or I/O, primarily because it doesn't seem to be running the table creation in parallel. It's working on one table fragment at a time. It also seems to be making a copy of the data in two places and leaving large portions the allocated data chunks unused. It's certainly not the way I would have written it, but then again I don't write database. The worst case is that these multiple copies of data will cause it to exceed the limits again and we'll have to start over. It looks like we're 68% of the way to exceeding those limits. Hope Informix is smart enough to avoid the problem.
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Message 1600685 - Posted: 13 Nov 2014, 17:28:01 UTC

If I recall rightly (and its a good few years since I last did anything in Informix) its ability to create, and then forget, orphan tables during a rebuild was "quite astounding" :-(
I'd believe the 25% figure too, and remember that time is non-linear....
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Message 1600707 - Posted: 13 Nov 2014, 18:09:04 UTC
Last modified: 13 Nov 2014, 18:17:13 UTC

Yeah well, it will take exactly the time it takes. Rome wasn't built in one day (or week) either.
Patience, patience....

Thanks Eric for then update though.
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Message 1600790 - Posted: 13 Nov 2014, 21:47:39 UTC

If complete rebuild inevitable maybe it's good time to think about different database engine, more optimal one (if such exits, of course...)
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Eric KorpelaProject Donor
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Message 1600846 - Posted: 14 Nov 2014, 0:19:11 UTC - in response to Message 1600790.  

Good idea. I'll have to dig into what features are found in the various database options.
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Message 1600901 - Posted: 14 Nov 2014, 3:24:29 UTC - in response to Message 1600846.  

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Message 1600922 - Posted: 14 Nov 2014, 4:41:29 UTC

Has anyone given any thought to contacting IBM concerning the Infomix limit problem? Maybe, just maybe they might have some insight into the problem, if someone were to ask nicely. Maybe we can get them on as a sponsor at same time.


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Message 1600957 - Posted: 14 Nov 2014, 7:04:05 UTC

Thanks for the heads-up Eric :)
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Message 1600960 - Posted: 14 Nov 2014, 7:07:18 UTC - in response to Message 1600922.  

Has anyone given any thought to contacting IBM concerning the Infomix limit problem? Maybe, just maybe they might have some insight into the problem, if someone were to ask nicely. Maybe we can get them on as a sponsor at same time.

That is definitely a good idea. Maybe there's nothing actually wrong with Informix, but S@H may be the first user to run into previously-unknown problems because of the size of the DB and the load and web of cross-references. The DB size and load has been well into "uncharted territory" for quite some time.

I remember reading a news post a few years ago mentioning MySQL was suffering some strange behavior and there were no clear answers as to why, simply because "nobody's ever made a DB that big with MySQL before."

So maybe contacting IBM and asking for some insight could not only resolve your own problems, but also result in preventing future problems for others.
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Message 1601024 - Posted: 14 Nov 2014, 10:50:57 UTC

Thanks Eric for the updates .

Don't understand a word you said but nice to know your on top of it.....:)

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Message 1601056 - Posted: 14 Nov 2014, 12:21:22 UTC - in response to Message 1601024.  

Thanks Eric for the updates .

Don't understand a word you said but nice to know your on top of it.....:)

I think it's like packing a suitcase when you go on holiday, first time you can't close it. Then you fold things differently and move stuff about till you can :)

Good luck with it Eric :)
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Message 1601070 - Posted: 14 Nov 2014, 13:35:34 UTC - in response to Message 1600960.  
Last modified: 14 Nov 2014, 14:13:55 UTC

Has anyone given any thought to contacting IBM concerning the Infomix limit problem? Maybe, just maybe they might have some insight into the problem, if someone were to ask nicely. Maybe we can get them on as a sponsor at same time.

That is definitely a good idea. Maybe there's nothing actually wrong with Informix, but S@H may be the first user to run into previously-unknown problems because of the size of the DB and the load and web of cross-references. The DB size and load has been well into "uncharted territory" for quite some time.

I remember reading a news post a few years ago mentioning MySQL was suffering some strange behavior and there were no clear answers as to why, simply because "nobody's ever made a DB that big with MySQL before."

So maybe contacting IBM and asking for some insight could not only resolve your own problems, but also result in preventing future problems for others.


I'm more familiar with DB2 than Informix as a database manager. Both have been used in data warehousing for years, DB2 has been using terabyte databases in particular. Unfortunately, DB2 requires a more hands on DBA. Since SQL is basically the same across all platforms and management systems, and MySQL is essentially using an extension of SQL; I would love to take a peek at our database/table schemas.

Another big problem that I see occurring is that Informix making data copies in multiple places while rebuilding the database, I've never heard or experienced that when rebuilding/restoring DB2 tables/databases. Since the rebuild/restore source is essentially the last full image copy (backup) merged with the succeeding incremental image copies, prior to the actual rebuild; then essentially it should be just a matter of copying one to another in an sequential manner. Once this is accomplished, there should be a log somewhere that has all of the current updates that were made to the table/database up to the time of the stoppage. Applying the log (LOGAPPLY) to the table/database will bring it current status. If necessary, the indices can be rebuilt using a REBUILD utility.


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Message 1601092 - Posted: 14 Nov 2014, 16:03:02 UTC

Thanks for the update, Eric. I wish I understood it on more than the most basic level.
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Message 1601141 - Posted: 14 Nov 2014, 18:30:22 UTC

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Message 1601293 - Posted: 15 Nov 2014, 2:24:09 UTC

New game for the Cafe... TLPTGAWUW!!!
(The last person to get a work unit wins)
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Message 1601299 - Posted: 15 Nov 2014, 2:43:52 UTC

I like that idea!
Pluto will always be a planet to me.

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Message 1601307 - Posted: 15 Nov 2014, 4:29:41 UTC - in response to Message 1601293.  

New game for the Cafe... TLPTGAWUW!!!
(The last person to get a work unit wins)

I thought we were already playing "First one to infinity wins" :P
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Message 1601322 - Posted: 15 Nov 2014, 5:09:42 UTC - in response to Message 1601293.  

New game for the Cafe... TLPTGAWUW!!!
(The last person to get a work unit wins)

Done :)
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Message boards : Technical News : Taking longer than expected (Nov 13, 2014)


 
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