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   ► MB LobbyCorel Paradox / ObjectPAL Coding BoardParadox Setup, Vista, etc. Topic   Print This     

Blob Binary Large Object Error

Blob Binary Large Object Error in Paradox Setup, Vista, etc. topic (part of our Corel Paradox / ObjectPAL Coding group).

Quick Search: Blob Binary   Blob Binary Large   Object Error  
Sam.S
North Hartland, VT USA
Rank: Ensign

I have been having a tough time with BLOB (Binary Large Object) errors in memo fields of some large tables running on a Win2008 R2 Terminal server with just 3 users.  Any one else have experience with this?

This is an app that has been running with support and modification for 25 years.

It has been running on this server for close to 8 years.

It is only accessed via a terminal server session, all activity in paradox is native to the server.

I have had the tables get corrupted 7 or 8 times in the last three weeks.  I have seen this probably 3 or four times before in the last 8 years, but a rebuild of the tables has resolved it.  In the last three weeks, I have not been able to go more than a couple of days without corruption.

I'll post more detail later, I wanted to get this up to see if others have experience with blob errors and figure out if this is the right Prestwood board to post it on as opposed to something specific to coding or tables.

Thanks

You want coffee?  I could write a paradox app for that...

 Posted 67 days ago (Thread Starter)
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Post ID #16667, 5 replies
Thread Started 5/17/2017 6:18:59 AM
View Counter=156
Last Reply Posted 5/22/2017 3:23:48 PM)
Location=North Hartland, VT USA 
Joined=7 years ago   MB Posts=37  
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Steven.G
Myrtle Beach, SC USA
Rank: Commander

blob/memo fields are not like regular fields, and are not directly part of a rebuild/repair.. conventional wisdom, over time, has been to avoid whenever possible.. a regular field with a full path name, pointing to a separate file, is much more stable.. (i.e. don't put a word doc in a blob field, put thename of the doc in a text field, and fire off Word itself)

and yes, I understand that such a change, this far down the road, probably isn't practical..

another potential repair option, if the blob contents only exist in the blob.. write a script that extracts the contents to files and/or to another table.. repair this table, reinsert the blob content

Steven Green
Senior Software Engineer
Paradox Support Specialist DOS/WIN

Prestwood IT Solutions
8421 Auburn Blvd, Suite 256, Citrus Heights, CA 95610
Office: 916-726-5675 | Fax: 916-726-5676 | http://www.prestwood.com
 Posted 67 days ago
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Post ID #16668 (Level 2) and Parent is 16667
Reply Posted 5/17/2017 6:49:44 AM
Location=Myrtle Beach, SC USA 
Joined=10 months ago   MB Posts=85  
Sam.S
North Hartland, VT USA
Rank: Ensign

Thanks for your feedback

My approach on repair has been similar to your extract and re-insert suggestion and the repairs have been successful. But then I have corruption again in a couple of days.

I have been really struggling to determine what is causing the failure. 

The memo fields have been reasonably stable for many years and this has been sudden onset, so I think there is a trigger somewhere if I can find it.

These memo fields are intended to hold text (Ansi 32 - 126) with the addition of carriage returns and tabs to allowing simple formating. 

One theory I have is users have unknowingly cut and pasted things into the memo fields that are not text (cut an past an address from a web page for example) and bad elements have ended up clogging up the memo fields. I have been working to crawl through all the data checking for 'illegal' characters or elements, anything out of ansi 32 - 126. That has not fixed it yet, but there is so much data, I have more work to do on that.

At the same time, I have been working to prevent or scrub pastes before letting them into the data.

I have also theorized that the tables have gotten too large to deal with.  But I have archive significant data, getting the table down to 80% of what has been manageable in the past.  That has not resolved the problem.

My last approach is that something is preventing paradox from having full control of the DB and MB files and they are getting out of sync. Something like backup taking control of the file while users are in it or maybe something like op locks.  I have made sure the backup is not running during the day and now I am excluding the Paradox directories from auto backup and manually backing them up daily. Again, no Joy.  I don't have any evidence that the server has been updated, patches on this server are done quartley for just this kind of conflict. I have considered a bad hard drive, but check disk didn't indicate any problems. I am at the point of adding another physical drive just  to rule that out, though.

You want coffee?  I could write a paradox app for that...

 Posted 67 days ago (Thread Starter)
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You want coffee?  I could write a paradox app for that...


Post ID #16669 (Level 3) and Parent is 16667
Reply Posted 5/17/2017 7:13:23 AM
Location=North Hartland, VT USA 
Joined=7 years ago   MB Posts=37  
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Steven.G
Myrtle Beach, SC USA
Rank: Commander

if they're out of sync, the date/time stamp will show that, and paradox will refuse to open the table

your use of the field is typical of many apps, simply expanding the capabilities of mostly-simple text.. the carraige returns and tabs aren't an issue.. over time, several things about memo fields -

the field should be the last field of the table structure

make the part that's in the table (the M#) be big enough to hold most of the little stuff, just like if it was an alpha field

on-going editing of this kind of "formatted text" field isn't good for stability

Steven Green
Senior Software Engineer
Paradox Support Specialist DOS/WIN

Prestwood IT Solutions
8421 Auburn Blvd, Suite 256, Citrus Heights, CA 95610
Office: 916-726-5675 | Fax: 916-726-5676 | http://www.prestwood.com
 Posted 66 days ago
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Post ID #16670 (Level 4) and Parent is 16667
Reply Posted 5/18/2017 4:48:35 AM
Location=Myrtle Beach, SC USA 
Joined=10 months ago   MB Posts=85  
Sam.S
North Hartland, VT USA
Rank: Ensign

Thanks for your input.

I still haven't been able to find a diffinitive cause of the blob error, but interestingly, I can run a delete query on it and the resulting DELETED.DB will contain the right number of recs with the Memo fields intact.  Running a Tutility repair/rebuild did not result in a viable resulting table, though.

I am thinking that there was something cut and pasted into the memo field that is choking paradox.  But it's like medusa, as soon as you look at the offending data in any way, the table turns to stone and sharters into a million pieces. That's the analogy I am going to give the users, anyway.

I am not out of the woods on this yet, but I think I have been able to cleanup the table to keep the users going and archived to memo information to an auxilliary table.  I also worked out code to intercept a cut/paste do ascan of the clipboard information and resolve it to simple text before allowing it to be pasted.  I am slowly adding the functionality back in as I continuously test for corruption.  I am pretty sure I have aworkable plan and approach in place.

You want coffee?  I could write a paradox app for that...

 Posted 62 days ago (Thread Starter)
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You want coffee?  I could write a paradox app for that...


Post ID #16673 (Level 5) and Parent is 16667
Reply Posted 5/22/2017 12:17:52 PM
Location=North Hartland, VT USA 
Joined=7 years ago   MB Posts=37  
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Steven.G
Myrtle Beach, SC USA
Rank: Commander

what happens when you add the deleted back, and query it out again? or add the good stuff to the deleted table?

just curious..

Steven Green
Senior Software Engineer
Paradox Support Specialist DOS/WIN

Prestwood IT Solutions
8421 Auburn Blvd, Suite 256, Citrus Heights, CA 95610
Office: 916-726-5675 | Fax: 916-726-5676 | http://www.prestwood.com
 Posted 62 days ago
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Post ID #16674 (Level 6) and Parent is 16667
Reply Posted 5/22/2017 3:21:25 PM
Location=Myrtle Beach, SC USA 
Joined=10 months ago   MB Posts=85  

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