As the log contains sufficient information about each transaction executed already, the database server should be able to recover the database cluster by replaying changes and actions in the transaction log in case of the server crash.
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 Postgre SQL, WAL is an acronym of Write Ahead Log.
The WAL mechanism was first implemented in version 7.1 to mitigate the impacts of server crashes.
It also made possible the implementation of the Point-in-Time Recovery (PITR) and Streaming Replication (SR), both of which are described in Chapter 10 and Chapter 11 respectively.
A transaction log is an essential part of database, because all of the database management system is required not to lose any data even when a system failure occurs.
It is a history log of all changes and actions in a database system so as to ensure that no data has been lost due to failures, such as a power failure, or some other server failure that causes the server crash.
Postgre SQL doesn’t support these features natively, but this temporal tables approximates them.This requires Postgre SQL 9.2 or higher, as that was the first version with support for a timestamp range data type.Before you dig in, it’s important to note that this extension does not provide complete support for the 2011 standard.We will not go into too much detail here since the install wizard (at least the windows one) is pretty good. You can use something like psql or the pg Admin query window to create a database and spatially enable your database.This is the way to go if you have only a terminal interface to your db or you have a butt load of extensions you want to enable.Postgre SQL is developed by the Postgre SQL Global Development Group. We need to install the , Java Development Kit, for compiling and running Java programs. If we are using Net Beans IDE, than we have already the driver at hand. Logger; public class Not Prepared $ javac zetcode/Not $ /usr/bin/time java -cp .:lib/postgresql.jdbc4zetcode.