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Lost Data |
Fri, Nov 2 2007 9:36 AM | Permanent Link |
Gordon Turner | I have a customer who entered data (employee information) into my
application, created a backup of her data (from within the app - create a zip file of the database files) and closed the application. Upon starting the app a couple days later, a number of employee entries were missing. Restoring from the backup (from within the app - overlaying the database files with the files contained in the zip file) did not restore the missing entries. The first group of employees she entered were still there, but none of the later entries. (She is the only user of the application.) This is the second or third customer who has reported this type of problem and it concerns be greatly. (The app is D7 using DBISAM 3.24 in stLocal mode.) I've looked at the backup file and the data in it seems internally consistent so it's hard to say it's because of a single corrupted file. (Running a repair on the tables did not show any problems being fixed.) I perform a FlushBuffers in the OnTableClose event for all tables and close all the tables before creating a backup file, so it's difficult to say it's a caching problem. The customer is running XP Pro SP2 and the data files and application are stored on her PC. Tim, I've posted the backup file she sent me in Binaries (only a handful of records in each table). Is there any way for you to tell if data has been deleted or if a repair has been performed on any of the tables? -- Gordon Turner Mycroft Computing http://www.mycroftcomputing.com |
Fri, Nov 2 2007 11:37 PM | Permanent Link |
Dave Harrison | Gordon Turner wrote:
> I have a customer who entered data (employee information) into my > application, created a backup of her data (from within the app - create > a zip file of the database files) and closed the application. Upon > starting the app a couple days later, a number of employee entries were > missing. Restoring from the backup (from within the app - overlaying > the database files with the files contained in the zip file) did not > restore the missing entries. The first group of employees she entered > were still there, but none of the later entries. (She is the only user > of the application.) > > This is the second or third customer who has reported this type of > problem and it concerns be greatly. (The app is D7 using DBISAM 3.24 in > stLocal mode.) I've looked at the backup file and the data in it seems > internally consistent so it's hard to say it's because of a single > corrupted file. (Running a repair on the tables did not show any > problems being fixed.) I perform a FlushBuffers in the OnTableClose > event for all tables and close all the tables before creating a backup > file, so it's difficult to say it's a caching problem. The customer is > running XP Pro SP2 and the data files and application are stored on her PC. > > Tim, I've posted the backup file she sent me in Binaries (only a handful > of records in each table). Is there any way for you to tell if data has > been deleted or if a repair has been performed on any of the tables? > Gordon, Maybe she entered the data in the wrong directory? Scan the drive looking for other *.DAT files that may have been created. Is there a test database she might have been using by mistake? Dave |
Sat, Nov 3 2007 6:07 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Gordon,
<< I have a customer who entered data (employee information) into my application, created a backup of her data (from within the app - create a zip file of the database files) and closed the application. Upon starting the app a couple days later, a number of employee entries were missing. Restoring from the backup (from within the app - overlaying the database files with the files contained in the zip file) did not restore the missing entries. The first group of employees she entered were still there, but none of the later entries. (She is the only user of the application.) >> As Dave indicated - is there any capability to use multiple databases ? That is usually the most likely culprit besides improper shutdowns or Vista issues with protected directories (which doesn't apply). << This is the second or third customer who has reported this type of problem and it concerns be greatly. >> I can assure 100% that DBISAM is not responsible for this issue. It does not "lose" data. << (The app is D7 using DBISAM 3.24 in stLocal mode.) I've looked at the backup file and the data in it seems internally consistent so it's hard to say it's because of a single corrupted file. (Running a repair on the tables did not show any problems being fixed.) >> It's possible with 3.x that an issue with the indexes might escape detection during the repair. 3.x wasn't as thorough as 4.x and later versions in terms of validating the indexes during a repair. <<im, I've posted the backup file she sent me in Binaries (only a handful of records in each table). Is there any way for you to tell if data has been deleted or if a repair has been performed on any of the tables? >> Which table is the one missing the records ? -- Tim Young Elevate Software www.elevatesoft.com |
Sun, Nov 4 2007 1:00 PM | Permanent Link |
"Robert" | "Tim Young [Elevate Software]" <timyoung@elevatesoft.com> wrote in message news:76B7BE19-FB32-439A-90D2-A2C378874EC3@news.elevatesoft.com... > Gordon, > > << I have a customer who entered data (employee information) into my > application, created a backup of her data (from within the app - create a > zip file of the database files) and closed the application. Upon starting > the app a couple days later, a number of employee entries were missing. > Restoring from the backup (from within the app - overlaying > the database files with the files contained in the zip file) did not > restore the missing entries. The first group of employees she entered > were still there, but none of the later entries. (She is the only user of > the application.) >> Never say never, but it does not sound at all like a DBISAM issue. Do you have a filter that was not reset, have you looked at the table with DBSYS, is it possible that you were doing the updates inside a transaction and you cancelled instead of comitting? Robert > > As Dave indicated - is there any capability to use multiple databases ? > That is usually the most likely culprit besides improper shutdowns or > Vista issues with protected directories (which doesn't apply). > > << This is the second or third customer who has reported this type of > problem and it concerns be greatly. >> > > I can assure 100% that DBISAM is not responsible for this issue. It does > not "lose" data. > > << (The app is D7 using DBISAM 3.24 in stLocal mode.) I've looked at the > backup file and the data in it seems internally consistent so it's hard to > say it's because of a single corrupted file. (Running a repair on the > tables did not show any problems being fixed.) >> > > It's possible with 3.x that an issue with the indexes might escape > detection during the repair. 3.x wasn't as thorough as 4.x and later > versions in terms of validating the indexes during a repair. > > <<im, I've posted the backup file she sent me in Binaries (only a handful > of records in each table). Is there any way for you to tell if data has > been deleted or if a repair has been performed on any of the tables? >> > > Which table is the one missing the records ? > > -- > Tim Young > Elevate Software > www.elevatesoft.com > |
Sun, Nov 4 2007 11:21 PM | Permanent Link |
Gordon Turner | Dave Harrison wrote:
> > Maybe she entered the data in the wrong directory? Scan the drive > looking for other *.DAT files that may have been created. Is there a > test database she might have been using by mistake? The user can only select a data directory when installing the application. That said, the path to the data files is stored in HKEY_CURRENT_USER. If the app does not find its data files, it creates a new set. So if, for some reason, her local userid changed, she might access a new set of data files. But that would only cover loosing all data, not later entries to the current data files. To loose later entries would require changing userIDs twice. And how would the older entries appear in the new set of data files? Very frustrating and confusing as I'm not sure how to reassure the customer that it won't happen again if I'm not sure how it happened in the first place. -- Gordon Turner Mycroft Computing http://www.mycroftcomputing.com |
Sun, Nov 4 2007 11:26 PM | Permanent Link |
Gordon Turner | Tim Young [Elevate Software] wrote:
> > As Dave indicated - is there any capability to use multiple databases ? > That is usually the most likely culprit besides improper shutdowns or Vista > issues with protected directories (which doesn't apply). > > << This is the second or third customer who has reported this type of > problem and it concerns be greatly. >> > > I can assure 100% that DBISAM is not responsible for this issue. It does > not "lose" data. > > << (The app is D7 using DBISAM 3.24 in stLocal mode.) I've looked at the > backup file and the data in it seems internally consistent so it's hard to > say it's because of a single corrupted file. (Running a repair on the > tables did not show any problems being fixed.) >> > > It's possible with 3.x that an issue with the indexes might escape detection > during the repair. 3.x wasn't as thorough as 4.x and later versions in > terms of validating the indexes during a repair. > > <<im, I've posted the backup file she sent me in Binaries (only a handful of > records in each table). Is there any way for you to tell if data has been > deleted or if a repair has been performed on any of the tables? >> > > Which table is the one missing the records ? The immediate problem is the Employee.dat table. The customer says she entered about 20 employees and when she started the app again, only the first 8 were still there. The process of entering an employee does involve a transaction as it updates multiple tables behind the scenes, so rolling back a single transaction could explain one missing employee, but not 10 - 10 separate transactions. From her email... I spent most of the day inputting information. By the end of the day, I had about 21 employees with 1 ½ yrs of information, many time off reasons and their benefit policies. When I finished at the end of the day, I backed up my information. When I logged on today, there were only the first 8 employees I posted and only 5 time off reasons. I tried to do a restore from my back up and it just backed it up to the same point of 8 employees. Is there any way to tell if my info is still there? What would cause this? .... A backup consists of closing all the tables in the database, and performing a ZIP of the data files. -- Gordon Turner Mycroft Computing http://www.mycroftcomputing.com |
Mon, Nov 5 2007 9:01 AM | Permanent Link |
Gordon Turner | Robert wrote:
> Never say never, but it does not sound at all like a DBISAM issue. Do you > have a filter that was not reset, have you looked at the table with DBSYS, > is it possible that you were doing the updates inside a transaction and you > cancelled instead of comitting? Thanks for the suggestions, but this is a program I've been selling for several years - 1000+ customers, and this is only the second customer of this app complaining about lost data. And although entering an Employee into the system involves a transaction, the failure to commit would not account for some records being saved and others not. (The user only clicks on an OK button to save the data.) -- Gordon Turner Mycroft Computing http://www.mycroftcomputing.com |
Mon, Nov 5 2007 9:20 AM | Permanent Link |
Gordon Turner | Sorry for the double response, but I forgot to add some things writing
late last night... Tim Young [Elevate Software] wrote: > > As Dave indicated - is there any capability to use multiple databases ? > That is usually the most likely culprit besides improper shutdowns or Vista > issues with protected directories (which doesn't apply). The app has multi-user capabilities, but the customer says the data files are located on her PC, which would mean only a single user. This is born out by only one record in the Users table. (The app requires a record in the Users table for each person accessing the data with the app.) > I can assure 100% that DBISAM is not responsible for this issue. It does > not "lose" data. I wasn't thinking DBISAM itself lost the data so much as perhaps it was a caching issue or a corruption problem. Sorry if I wasn't clear about this. The app tests for corruption by examining the TextIndexStopWords property before opening the tables and if an of a number of corruption EDBISAMEngine errors occurs, attempts a repair of the data files. The session component has its LockProtocol set to lpPessimistic and the setup program sets the following HKEY_LOCAL_MACHINE values... System\CurrentControlSet\Services\LanmanServer\Parameters CachedOpenLimit = 0 EnableOpLocks = 0 System\CurrentControlSet\Services\LanmanWorkstation\Parameters UseOpportunisticLocking = 0 UtilizeNtCaching = 0 The customer is running Windows XP Pro SP2. -- Gordon Turner Mycroft Computing http://www.mycroftcomputing.com |
Mon, Nov 5 2007 9:27 AM | Permanent Link |
"Robert" | "Gordon Turner" <gordon@mycroftcomputing.com> wrote in message news:A6057034-B4A0-4588-9AC7-4F969C0EA555@news.elevatesoft.com... > Robert wrote: >> Never say never, but it does not sound at all like a DBISAM issue. Do you >> have a filter that was not reset, have you looked at the table with >> DBSYS, is it possible that you were doing the updates inside a >> transaction and you cancelled instead of comitting? > > Thanks for the suggestions, but this is a program I've been selling for > several years - 1000+ customers, and this is only the second customer of > this app complaining about lost data. And although entering an Employee > into the system involves a transaction, the failure to commit would not > account for some records being saved and others not. (The user only > clicks on an OK button to save the data.) > Careful, once you assume that it is a DBISAM problem, you stop looking for the possible real cause. DBISAM is in use in many places, and it does not lose data. The failure to commit could VERY WELL account for the situation you described. They entered one group without problems, the second group failed 100%. It is possible something went wrong with an update, with opening the tables, who knows, some flag was set incorrectly and, from that point on, every transaction on the second update was cancelled intead of being committed. IOW, debugging 101, "if I wanted to make this happen, how would I do it?" Have you followed carefully and without prejudices every path that can lead to cancelling (or not committing) the transaction? Robert |
Mon, Nov 5 2007 1:11 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Gordon,
<< But that would only cover loosing all data, not later entries to the current data files. To loose later entries would require changing userIDs twice. >> You are correct. << And how would the older entries appear in the new set of data files? >> They wouldn't, given the scenario that you outline. -- Tim Young Elevate Software www.elevatesoft.com |
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