I have been through many articles talking about primary reasons about the MS Access DB corruption like :
Hardware or software related issues.
Multiple Users are accessing Database concurrently.
The system is infected by Viruses / Worms.
Faulty Access database design or structure.
An inappropriate shutdown of the local machine
I would like to know if there's a way to determine the actual cause (like Network failure, multi-user access, incorrectly exited the DB etc.) of the DB corruption each time it happened by may be by looking at some logs or so.
Your list can be reduced to:
Network, disk, or OS related issues
The system is infected by malware
Access crashed
An inappropriate shutdown of the local machine
But there is no log or similar to tell the actual cause.
Related
I've been programming for just a few years, and we have a default dll used for data access. It seems like there has been some data-mining or site scraping going on here lately, and although there are no issues with our SQL database connections, many of the programs that access the as/400 are keeping connections open and idle for long periods of time. I looked through our default data access dll and added code to close the connection after each function, but that didn't help. I have little experience with db2 / as/400 ... how do I close all of these open / idle connections from the code?
If you're using connections pools, that's working as designed.
Are you sure the connection is actually open? How are you determining that?
If you're just seeing locks held by the QZDASOINIT job on the IBM i, then that's also by design. The system will hard close tables (cursors) after the first use. When used again by the same job, the system will only pseudo-close them; in order to provide faster response when they are re-used.
If an operation needing exclusive access is attempted, the system will hard close the pseudo closed cursor.
It is found that some BizTalk Receive Locations are disabled after server reboot (BizTalk server and SQL Server are separately installed to different physical servers)
Is there any idea on this scenario? Due to the boot sequence or other issues?
I will assume that, once you enable the receive locations manually, they are working correctly.
Typically, when FILE receive locations fail while pointing to an external server/share, it is because they are no longer available.
Make sure that, during the night, there are no network issues, planned/unplanned downtime of the share (= here your SQL server). A BizTalk receive location will retry to access a share for quite a while before disabling itself. Check the event log(s) for more information. You would want to look for errors/warnings there indicating an issue with connectivity between BizTalk and SQL.
Another issue might be that there are too many connections between your BizTalk server and SQL server. You can provide a maximum number of connections in the FILE share properties.
Also, you could try this link: https://serverfault.com/questions/235032/intermittent-connection-to-windows-7-shared-folder-from-windows-xp-workstations
It describes a potential fix for optimizing throughput for file sharing, although it depends on your operating system.
I open the database file and obtain a database connection using open() method of sqlite3 and the connection will not be closed until program exits. If there occurs an unexpected error such as computer's suddenly power-off or OS crash, will the mode of the database file be damaged, or its handle lost? More specifically, can it remain writable if I reboot my computer? BTW, I don't care about the data loss when errors occurs.
Thank you very much!
SQLite is specifically designed to protect against this. From the official SQLite is Transactional page:
All changes within a single
transaction in SQLite either occur
completely or not at all, even if the
act of writing the change out to the
disk is interrupted by
a program crash,
an operating system crash, or
a power failure.
The claim of the previous paragraph is
extensively checked in the SQLite
regression test suite using a special
test harness that simulates the
effects on a database file of
operating system crashes and power
failures.
You might also be interested in the SQLite article Atomic Commit in SQLite if you need to know the specific details on how they protect against crashes such as the above.
Regarding writing after a crash: (from File Locking and Concurrency)
A hot journal is created when a process is in the middle of a database update and a program or operating system crash or power failure prevents the update from completing. Hot journals are an exception condition. Hot journals exist to recover from crashes and power failures. If everything is working correctly (that is, if there are no crashes or power failures) you will never get a hot journal.
The worst that can happen will be that you need to delete the hot journal that is left over after a crash.
As Sqlite is ACID-compliant, a power-off shouldn't be an issue.
http://en.wikipedia.org/wiki/ACID
anything could potentially happen on sudden power off. However I'd suggest UPS to mitigate any risk.
a few days we had a strange error with sqlite. We use a sqlite database on a network share with several computers accessing it. Our client reported, that the database is gone. A quick overview showed, that the database was still there but no computer could access it. It also showed a s3db-journal file indicating that someone is/was accessing the db when something happened. The thing that is strange - the s3db-journal file was locked by the file system (we could not copy/delete it). After restarting all applications, the locked file disappeared as it should be.
How does this happen? We would like to deduct somehow how our client got into this situation. We know, that there was a corrupt network cabeling to one of the computers.
Thank you for your help.
Tobias
To clarify this: several = up to 10 computer
From the "Appropriate uses for SQLite" page:
If you have many client programs accessing a common database over a network, you should consider using a client/server database engine instead of SQLite. SQLite will work over a network filesystem, but because of the latency associated with most network filesystems, performance will not be great. Also, the file locking logic of many network filesystems implementation contains bugs (on both Unix and Windows). If file locking does not work like it should, it might be possible for two or more client programs to modify the same part of the same database at the same time, resulting in database corruption. Because this problem results from bugs in the underlying filesystem implementation, there is nothing SQLite can do to prevent it.
A good rule of thumb is that you should avoid using SQLite in situations where the same database will be accessed simultaneously from many computers over a network filesystem.
It very well might be a bug in the network filesystem you're using. Either way, the SQLite developers explicitly recommend against using databases on network filesystems.
The issue is resolved. The database-component (zeos) threw an exception and we tried a rollback. Due to the way the component was designed, this is only allowed when you started a transaction. If you don't you get the locked s3db-journal file.
In the end we learned 2 things: never rollback when you did not start a transaction, second - there is a function InTransaction from zeos for that.
I have an application with a file receive location. After the host instance has been running for a few hours the receive location fails to identify new files dropped into the folder that it is monitoring. It doesn't forget about them altogether, it's just that performance grinds to a crawl. The receive location is configured to poll the target folder every 60 seconds but after host instance has been running for an hour or so, then it seems that the target folder is being polled only every thirty minutes. If I restart the host instance then the files waiting in the target folder are collected right away and performance is fine for the next hour or so.
The same application runs fine in a different environment.
There are now obvious entries in the event log related to the problem.
All the BizTalk SQL jobs are running fine except for Backup BizTalk Server (BizTalkMgmtDb).
Any suggestions gratefully received.
Thanks
Rob
Here are some additional tools which may help you identify and diagnose BizTalk database issues.
BizTalk MsgBox Viewer
Here is a tool to repair identified errors:
Terminator
Use at your own risk... read the glogs and docs. Start with the message box viewer and let us know our results.
Without more details, the biggest tell is that your Backup Job is failing. If the backup job is failing, it may not be properly configured. If it is properly configured and still failing, then you've got other issues. Can you give us some more information about your BizTalk install.
What version are you running?
What are our database sizes?
What are your purge and archive settings like?
Is there any long running blocks in your SQL Server DB coming from BizTalk?
Another thing to consider is the user accounts the send, receive and orchestration hosts are running under. Please check the BizTalk Administration Console. If they are all running the same account, sometimes the orchestrations can starve the send and receive processes of CPU time. I believe priority is given to orchestrations then receive, then send. Even if you are just developing, it is useful to use separate accounts for this. This also improves security.
The Wrox BizTalk Server 2006 will also supply tuning advice.
What other things are going on with the server? Is BizTalk pegged otherwise or is it idle?
You mention that the solution does not have any problems in another environment, so it's likely that there is a configuration problem.
Check the following:
** On SQL Server, set some upper memory limit for SQL Server. By default, SQL Server uses whatever it can get and then hangs onto it, so set a reasonable limit so that your system can operate without spending a lot of time paging memory onto and from your hard drive(s).
** Ensure that you have available disk space - maybe you are running low - this can lead to all kinds of strange problems.
** Try to split up the system's paging file among its physical drives (if you have more than one drive on the system). Also consider using a faster drive, or if you have lots of cash laying around, get a SAN.
** In BizTalk, is tracking enabled? If so, are you also tracking message bodies? Disable tacking or message body tracking and see if there is a difference.
** Start performance monitor and monitor the following counters when running your solution
Object: BizTalk Messaging
Instance: (select the receiving host) %%
Counter: Documents Received/Sec
Object: BizTalk Messaging
Instance: (select the transmitting host) %%
Counter: Documents Sent/Sec
Object: XLANG/s Orchestrations
Instance: (select the processing host) %%
Counter: Orchestrations Completed/Sec.
%% You may have only one host, so just use it. Since BizTalk configurations vary, I am using generic names for hosts.
The preceding counters monitor the most basic aspects of your server, but may help to narrow down places to look further. You can, of course, add CPU and Memory too. If you have time (days...maybe weeks) you could monitor for processes that allocate memory and never release it. Use the following counter...
Object: Memory
Counter: Pool Nonpaged Bytes
Slow decline of this counter indicates that a process is not releasing memory, which affects everything on the system.
Let us know how things turn out!
I had the same problem with, when my orchestration was idle for some time it took a long time to process the first msg. A article of EvYoung helped me solve this problem.
"This is caused by application domain unloading within the BizTalk host process. If an AppDomain is shutdown after idle, the next message that comes needs to wait for the Orchestration to compile again. Depending on the complexity of your design, this can be a noticeable wait. To prevent this in low latency requirement scenario, you can modify the BTSNTSVC.EXE.config file and set SecondsIdleBeforeShutdown property to -1. This will prevent AppDomain shutdown due to idle."
You can find the article in here:
http://blogs.msdn.com/b/biztalkcpr/archive/2008/05/08/thoughts-on-orchestration-performance.aspx
It took me to long to respond but i thought i might help someone. cheers :)
Some good suggestions from others. I will add :
Do you have any custom receive pipeline components on the receive location ? If so perhaps one is leaking memory, calling some external component eg database which is taking a long time ?
How big are the files you are receiving ?
On the File transport properties of your receive location, set "file renaming" on, do the files get renamed within 60s.