- Aug 28, 2012
SQLite is an Open Source database, which is zero-configuration, compact, server less, SQL database engine. S-Q-L-ite refers to lighter version of SQL and its Database creation can be done by many languages like, C, C++, C#, Python, Basic, Java, and Delphi. SQLite is of very small size so it can also be used in embedded systems such as Android, iOS, Symbian OS, WebOS, and Maemo. We cannot view our SQLite database such as cookies created by browser, apps and cached copy of website data; if your data is being corrupted then we need software to view it. Reasons of Corruption – There may be various possible reasons by which the database of SQL is being corrupted. They are – File Overwritten – Since SQLite database files are ordinary disk files, so any of the process can open it and write on it. SQLite library is unable to overcome from these situations. This contains some reasons as described below. Continuity of Using File Descriptor Even it is Closed – If a file descriptor is opened on a file and after some time it is closed and again opened on SQLite database. Now, a new thread starts writing into the old file descriptor without realizing that the old file is already closed. In this case, the data goes to the server is replaced and leads to corruption. Backup During Transaction of Data – Since backup of data runs in background so there is a possibility that the backup process takes place during the transaction. It leads to the backup of mix of some new and some old i.e. the data in backup file is of corrupted data. Deletion of Hot Journal – If the transaction fails due to crash or power failure then we need an auxiliary journal files having the same name with the addition of –journal or –wal suffix to roll back this transaction. But the automatic recovery is not possible if these journal files are deleted, moved or renamed after crash or power failure. Problem of File Locking – SQLite locks the database file to avoid changes done by two different processes to coordinate concurrent process. This may cause to data corruption. Missed or Broken Lock Details – To perform locking, SQLite depends upon the underlying file system but sometimes the logic used for lock does not behave well with NFS files. If the locking system contains un-resolvable bugs, and two or more processes try to access that database at the same time then data corruption may arise. POSIX Advisory Locks Cancelled – POSIX Advisory Locking is the default mechanism used for locking in UNIX. The problem arises when the close() system call cancel all the POSIX advisory locks on the same file for all threads and file descriptors in the process. Contradiction of two locking Protocols – To handle the database, SQLite3 vfs and SQLite3 open v2() are two important protocols. If a system works on these protocols together then chances of contradiction is very high. Remove or Rename Database Link – If we rename the actual SQLite database file and it is not located at the same location then it will be responsible to the corruption of database. Many links for a single database File – If a single database is associated with various links in network connectivity then this is also considered as reason for corruption. Database not synchronizing – If the database is not synchronizing in SQLite or we can say if there is the violation of ACID properties then this leads to database corruption. Disk Drives are not praising Sync Request – If the disk is broken then there is no option to deal with it. To prevent this reason, the user should always use SQLite WAL mode. Restrain the Data Sync using PRAGAMAs – Synchronization is not performed if the PRAGAMA setting is in OFF state. Disk Drive and Flash Drive Failures – For any reason, if the drive is crashed or failed then SQLite database will result in corruption. Lack of Data Storage Capacity – If the disk has no more space to save the data and the user still trying to write on it then corruption may take place. Uncertainty with Flash Memory Controllers – If the format of SQLite database is changed to different format if hard drive is not power protected. Memory Corruption – SQLite and its application has the same address space. It means that buffer overruns, stray pointers, heap corruption and other malfunctions of the application can corrupt the internal data structure of SQLite. These will result to a corrupted database file. The memory corruption problem occurs when memory – mapped I/O is used. Conclusion – Above are the reasons for corruption of database files, any other reason may also be a cause to corruption of SQLite database. To prevent from these situations, try not to let them happen. In most of the above situations, we cannot deal manually to resolve them so you can take the advantage of SQLite Viewer to recover and view the SQLite database. Some of the software is completely free and some of them work on purchasing.