We have data stored in encrypted fields (with SQL Server encryption) in our database and we have a requirement to be able to remove certain records from our database under certain peculiar conditions that I will spare you. However it has been noted by a DBA that simply nulling out the data potentially still leaves residual data in the file so it could potentially be recovered.
It has been suggested by someone in the team that (rather than nulling) we write a '*' for each character we want to remove then delete the record, and they assert that this will wipe the data so if someone gets hold of the mdf file the value won't be retrievable (because the bits have been overwritten). For example if we have a value "abc" we run an update statement that replaces this value with '***'. Then we delete the record.
Can anyone confirm if this is the case? Personally I'm skeptical, but I'm a developer and not a DBA so this isn't an area of specialty for me.
Related
My company has a really old Access 2003 .ADP front-end connected to an on-premise SQL Server. I was trying to update the front-end to MS Access 2016, which is what we're transitioning to, but when linking the tables I get all the fields in this specific table as #Deleted. I've looked around and tried to change some of the settings, but I'm really not that into SQL Server to know what I'm doing, hence asking for help.
When converting the table to local, all the info is correctly displayed, so it begs the question. Also, skipping to the last record will reveal the info on that record, or sorting/filtering reveals some of the records, but most of the table stays "#Deleted"...
Since I know you're going to ask: Yes, I need to edit the records.. Although the snapshot method would work for people trying to view the info, some of us need to edit it.
I'm hoping someone can shed some light on this,
Thanks in advance, Rafael.
There are 3 common reasons for this:
You have bit fields in SQL server, but they are null. They should be assigned a default of 0.
The table in question does NOT have a PK (primary key).
Last but not least you need (want) to add a timestamp column. Keep in mind that this is really what we call a “row version” column (so it not a date/time column, but a timestamp column). Adding this column will help access determine if a record been changed, and this is especially the case for any table/form in Access that allows editing of “real” number data types (single, double). If access does not find a timestamp column, then it reverts to a column by column comparison to determine table changes, and due to how computers handle “real” numbers (with rounding), then such comparisons often fail.
So, check for the above 3 issues. You likely should re-run the linked table manager have making any changes.
I have a db containing info for a party.
I have a look-up field for who invited them, this is just a list of 4 names.
When I change this it changes characters in the last name column of the same row to ones that weren't even in the normal Latin alphabet.
The reverse happened as when I went to change it back it then changed the invited by column into some Chinese (looking) characters, breaking it's own validation as I said only items in the list were allowed, but it was fine with that for some reason.
Any idea what could be going on in this situation?
Also when I create a new table it doesn't appear in the Access Objects list until I reopen the database
The issue seems to have been caused by some corruption in the Access database file. Performing a "Compact and Repair Database" operation in Access appears to have resolved it.
I have a huge database (800MB) which consists of a field called 'Date Last Modified' at the moment this field is entered as a text data type but need to change it to a Date/Time field to carry out some queries.
I have another exact same database but with only 35MB of data inside it and when I change the data type it works fine, but when I try to change data type on big database it gives me an error:
Micorosoft Office Access can't change the data type.
There isn't enough disk space or memory
After doing some research some sites mentioned of changing the registry file (MaxLocksPerFile) tried that as well, but no luck :-(
Can anyone help please?
As John W. Vinson says here, the problem you're running into is that Access wants to hold a copy of the table while it makes the changes, and that causes it to exceed the maximum allowable size of an Access file. Compacting and repairing might help get the file under the size limit, but it didn't work for me.
If, like me, you have a lot of complex relationships and reports on the old table that you don't want to have to redo, try this variation on #user292452's solution instead:
Copy the table (i.e. 'YourTable') then paste Structure Only back
into your database with a different name (i.e. 'YourTable_new').
Copy YourTable again, and paste-append the data to YourTable_new.
(To paste-append, first paste, and select Append Data to Existing
Table.)
You may want to make a copy of your Access database at this point,
just in case something goes wrong with the next part.
Delete all data in YourTable using a delete query---select all
fields, using the asterisk, and then run with default settings.
Now you can change the fields in YourTable as needed and save
again.
Paste-append the data from YourTable_new to YourTable, and check
that there were no errors from type conversion, length, etc.
Delete YourTable_new.
One relatively tedious (but straightforward) solution would be to break the big database up into smaller databases, do the conversion on the smaller databases, and then recombine them.
This has an added benefit that if, by some chance, the text is an invalid date in one chunk, it will be easier to find (because of the smaller chunk sizes).
Assuming you have some kind of integer key on the table that ranges from 1 to (say) 10000000, you can just do queries like
SELECT *
INTO newTable1
FROM yourtable
WHERE yourkey >= 0 AND yourkey < 1000000
SELECT *
INTO newTable2
FROM yourtable
WHERE yourkey >= 1000000 AND yourkey < 2000000
etc.
Make sure to enter and run these queries seperately, since it seems that Access will give you a syntax error if you try to run more than one at a time.
If your keys are something else, you can do the same kind of thing, but you'll have to be a bit more tricky about your WHERE clauses.
Of course, a final thing to consider, if you can swing it, is to migrate to a different database that has a little more power. I'm guessing you have reasons that this isn't easy, but with the amount of data you're talking about, you'll probably be running into other problems as well as you continue to use Access.
EDIT
Since you are still having some troubles, here is some more detail in the hopes that you'll see something that I didn't describe well enough before:
Here, you can see that I've created a table "OutputIDrive" similar to what you're describing. I have an ID tag, though I only have three entries.
Here, I've created a query, gone into SQL mode, and entered the appropriate SQL statement. In my case, because my query only grabs value >= 0 and < 2, we'll just get one row...the one with ID = 1.
When I click the run button, I get a popup that tells/warns me what's going to happen...it's going to put a row into a new table. That's good...that's what we're looking for. I click "OK".
Now our new table has been created, and when I click on it, we can see that our one line of data with ID = 1 has been copied over to this new table.
Now you should be able to just modify the table name and the number values in your SQL query, and run it again.
Hopefully this will help you with whatever tripped you up.
EDIT 2:
Aha! This is the trick. You have to enter and run the SQL statements one at a time in Access. If you try to put multiple statements in and run them, you'll get that error. So run the first one, then erase it and run the second one, etc. and you should be fine. I think that will do it! I've edited the above to make it clearer.
Adapted from Karl Donaubauer's answer on an MSDN post:
Switch to immediate window (Ctl + G)
Execute the following statement:
DBEngine.SetOption dbMaxLocksPerFile, 200000
Microsoft has a KnowledgeBase article that addresses this problem directly and describes the cause:
The page locks required for the transaction exceed the MaxLocksPerFile value, which defaults to 9500 locks. The MaxLocksPerFile setting is stored in the Windows registry.
The KnowledgeBase article says it applies to Access 2002 and 2003, but it worked for me when changing a field in an .mdb from Access 2013.
It's entirely possible that in a database of that size, you've got text data that won't convert to a valid Date/Time.
I would suggest (and you may hate me for this) that you export all those prospective date values from "Big" and go through them (perhaps in Excel) to see which ones are not formatted the way you'd expect.
Assuming that the error message is accurate, you're running up against a disk or memory limitation. Assuming that you have more than a couple of gigabytes free on your disk drive, my best guess is that rebuilding the table would put the database (including work space) over the 2 gigabyte per file limit in Access.
If that's the case you'll need to:
Unload the data into some convenient format and load it back in to an empty database with an already existing table definition.
Move a subset of the data into a smaller table, change the data type in the smaller table, compact and repair the database, and repeat until all the data is converted.
If the error message is NOT correct (which is possible), the most likely cause is a bad or out-of-range date in your text-date column.
Copy the table (i.e. 'YourTable') then paste just its structure back into your database with a different name (i.e. 'YourTable_new').
Change the fields in the new table to what you want and save it.
Create an append query and copy all the data from your old table into the new one.
Hopefully Access will automatically convert the old text field directly to the correct value for the new Date/Time field. If not, you might have to clear out the old table and re-append all the data and use a string to date function to convert that one field when you do the append.
Also, if there is an autonumber field in the old table this might not work because there is no way to ensure that the old autonumber values will line up with the new autonumber values that get assigned.
You've been offered a bunch of different ways to get around the disk space error message.
Have you tried adding a new field to your existing table using Date data type and then updating the field with the value the existing string date field? If that works, you can then delete the old field and rename the new one to the old name. That would probably take up less temp space than doing a direct conversion from string to date on a single field.
If it still doesn't work, you may be able to do it with a sceond table with two columns, the first long integer (make it the primary key), the second, date. Then append the PK and string date field to this empty table. Then add a new date field to the existing table, and using a join, update the new field with the values from the two-column table.
This may run into the same problem. It depends on number of things internal to the Jet/ACE database engine over which we have no real control.
I have a database that I just converted the back end to SQL Server using SSMA. I left the front end in MS Access. I only converted the tables and not the queries. It already had some data in it and that moved over just fine.
All was going well until just recently. On opening the database and loading the main form Event Interest it started having problems with the first record of the subform, called Names. The first field in the first record has data sometimes and not others. This is a text field. When data is in the field it puts in random numbers. I believe they may be related to SQL somehow. When there is no data/missing you can select the field and hit the backspace button and the data will appear minus the one character you just errased. I have no idea what is going on.
Any help you can supply I would greatly appreciate it. Thank you in advance.
I am new to SQL Server and I have used older versions of MS Access for a few years.
I am not certain what the problem might be, but these are some considerations that come to mind:
try deleting and recreating your linked tables. Perhaps an update to the table structure (or view, if you're linked to a view) has invalidated some of the metadata stored in the table link in your front end.
does your table have a primary key? If not, you really need one. There really is no such thing as a properly-designed data table in a relational database that is PK-less.
does your table have a timestamp? If not, add one, as this helps Access keep track of whether or not the data has changed on the server.
However, let me add that none of these issues manifest themselves exactly with the symptoms you've described, so they may not help.
I have some SQL Server DTS packages that import data from a FoxPro database. This was working fine until recently. Now the script that imports data from one of the FoxPro tables bombs out about 470,000 records into the import. I'm just pulling the data into a table with nullable varchar fields so I'm thinking it must be a weird/corrupt data problem.
What tools would you use to track down a problem like this?
FYI, this is the error I'm getting:
Data for source column 1 ('field1') is not available. Your provider may require that all Blob columns be rightmost in the source result set.
There should not be any blob columns in this table.
Thanks for the suggestions. I don't know if it a corruption problem for sure. I just started downloading FoxPro from my MSDN Subscription, so I'll see if I can open the table. SSRS opens the table, it just chokes before running through all the records. I'm just trying to figure out which record it's having a problem with.
Cmrepair is an excellent freeware utility to repair corrupted .DBF files.
Have you tried writing a small program that just copies the existing data to a new table?
Also,
http://fox.wikis.com/wc.dll?Wiki~TableCorruptionRepairTools~VFP
My company uses Foxpro to store quite a bit of data... In my experience, data corruption is very obvious, with the table failing to open in the first place. Do you have a copy of foxpro to open the table with?
At 470,000 records you might want to check to see if you're approaching the 2 gigabyte limit on FoxPro table size. As I understand it, the records can still be there, but become inaccessible after the 2 gig point.
#Lance:
if you have access to Visual FoxPro command line window, type:
SET TABLEVALIDATE 11
USE "YourTable" EXCLUSIVE && If the table is damaged VFP must display an error here
PACK && To reindex the table and deleted "marked" records
PACK MEMO && If you have memo fields
After doing that, the structure of the table must ve valid, if you want to see fields with invalid data, you can try:
SELECT * FROM YourTable WHERE EMPTY(YourField) && All records with YourField empty
SELECT * FROM YourTable WHERE LEN(YourMemoField) > 200 && All records with a long memo field, there can be corrupted data
etc.
Use Repair Databases from my site (www.shershahsoft.com) for FREE (and Will always be FREE).
I have designed this program to repair damaged Foxpro/FoxBase/Dbase files. The program is very quick. It will repair 1 GB table in less than a minute.
You can asign files, and folders to the program. As you start the program it will mark all the corrupted files, and by clicking Repair or Check and Repair button, it will repair all the corrupted files. Moreover, it will create a folders "CorruptData" in the folders where the actual data exist, and will keep copies of the corrupt files there.
One thing to keep in mind, always run Windows CheckDsk on the drives where you store the files. Cause, when records are being copied to a table and power failure occures, there exists lost clusters which Windows converts to files during CheckDsk. After that, the RepairDatabases will do the job for you.
I have used many paid and free programs which repair tables, but all such programs leave extra records in the tables with embiguit characters (and they are time consuming too). The programer needs to find and delete such records manually. But Repair Databases actually recovers the original records, you need no further action. The only action you need is reindexing your files.
In the repair process some times File Open Dialog appears which asks to locate the compact index file for a table with indeces. You may click cancel the dialog at that point, the table will be repaired, however, you will need to reindex the file later. (this dialog may appear several times depending upon the number of corrupted indeces.)