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Begins transaction logging.
The database in which you want to start transaction logging.
Separate changes that must be applied together are considered to be a transaction. For example, transferring money from one account to another means debiting one account and crediting another. If for whatever reason one of those two changes cannot be done, the whole transaction is considered a failure and any change that was made must be undone.
Transaction logging records all the changes made to all the tables in a database. If no errors are encountered while making the individual changes in the transaction, the transaction log is cleared with the commit( ) method and the transaction is done. If an error is encountered, all changes made so far are undone by calling the rollback( ) method.
Transaction logging differs from caching updates in that changes are actually written to the disk. This means that others who are accessing the database can see your changes. In contrast, with cached updates your changes are written all at once later, when and if you decide to post the changes. For example, if you’re reserving seats on an airplane, you want to post a reservation as soon as possible. If the customer changes their mind, you can undo the reservation with a rollback. With cached updates, the seat might be taken by someone else between the time the data entry for the reservation begins and the time it is actually posted.
All locks made during a transaction are maintained until the transaction is completed. This ensures that no one else can make any changes until the transaction is committed or abandoned.
For SQL-server databases, the Database object’s isolationLevel property determines the isolation level of the transaction.
A Database object may have only one transaction active at one time; you cannot nest transactions.