Write ahead logging in dbms examples

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Write ahead logging in dbms examples

write ahead logging in dbms examples

I will refer to them here as OleDb and Odbc, as this is how their namespaces are spelled in the. As we shall see, however, there are situations where OleDb may be preferrable.

There is even the odd case where Odbc is the best choice, but as I will detail later, you do best to avoid Odbc when connecting to SQL Server. The three data providers have some common characteristics when it comes to handling of errors and messages from SQL Server, but there are also significant differences.

I will first cover the common features. To invoke a stored procedure from ADO. Net, you need a Command object. Net, and I list them here in the order you are most likely to use them: The are several overloaded Fill methods, some of which permit you to pass a CommandBehavior to specify that you want key or schema information, or that you want only a single row or a single result set.

ExecuteNonQuery Performs a command that does not return any result set or if it does, you are not interested in it.

One example is a store procedure that updates data. If there are several result sets, you use. NextResult to traverse them.

Simple Approach

This is the most general method to access data. Also here you can specify CommandBehavior. ExecuteScalar Use this method to run a command that produces a result set of a single value.

Network Admin Issues: Every RAC cluster requires a minimum of three separate networks and, built properly, four with a total of eight separate connectors and eight separate physical switches. In addition, it should be forced to update the log files first and then have to write the data into DB. i.e.; in ATM withdrawal, each stages of transactions should be . In the field of computer science, WAL is an acronym of Write Ahead Logging, which is a protocol or a rule to write both changes and actions into a transaction log, whereas in PostgreSQL, WAL is an acronym of Write Ahead leslutinsduphoenix.com the term is used as synonym of transaction log, and also used to refer to an implemented mechanism related to .

To test the possible variations, I wrote a simple application in VB. Net, from which I could pass an SQL command or a stored procedure, and select which data provider and which call method to use. For most of the tests, I used a procedure that depending on input parameters would produce results sets, informational or error messages, possibly interleaved.

What follows is based on my observations when playing with this application. If an error occurs during execution of a stored procedure, the method you used to invoke the procedure will raise an exception.

Thus, you should always call these methods within a Try-Catch block, so that you can handle the error message in some way. In the exception handler you have access to a provider-specific Exception object with an ErrorCollection, that containts information about the error.

What information that is available is specific for the provider. It seems, though, if there are both errors and informational messages, that the informational messages comes with the exception.

In the event handler, too, you have access to the ErrorsCollection from where you can retrieve the individual messages. As long as you stick to Fill, ExecuteNonQuery and ExecuteScalar, your life is very simple, as all data has been retrieved once you come back, and if there is an error you wind up in your exception handler.

If you want the return value of a stored procedure or the value of output parameters, these are available in the Parameters collection. However, the OleDb and Odbc providers normally do not fill in these values, if an error occurs during execution of a stored procedure. If you use ExecuteReader, there are a few extra precautions.

If the stored procedure first produces a result set, and then a message, you must first call. NextResult before you get an exception, or, for an informational message, any InfoMessage event handler is invoked.

However, under some circumstances, errors and messages may give cause to extraneous result sets. NextResult throws an exception, it does not return a value, so if you have something like: Net programmer, but this is my observation.BC is a leading publisher of Oracle articles and we are affiliated with Rampant TechPress, the leading publisher of Oracle leslutinsduphoenix.com you want to publish an article or book, please call or e-mail BC today.

write ahead logging in dbms examples

Write Ahead Logging (WAL) Remember the purpose of the transaction log is provide a write ahead log so the rules of A (Atomicity) D (Durability) of ACID can be maintained. the data files and as such we have the minimum LSN in the transaction log that needs to be active in order to provide database recovery.

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