Circular logging is a method of writing to the transaction log files that allows the data in a file to be overwritten after it has been committed to the database.
When circular logging is enabled, Exchange Server 2003 uses four transaction log files at a time. When the fourth log is full, the ESE begins to reuse the first log file thus saving space by not creating another log file.
The virtual address space is that finite amount of memory that can be addressed by the store.exe process on the Exchange server and, in most cases, dictates the overall performance and scalability of the server.
By default, 2GB of address space is reserved for Kernel mode and 2GB is reserved for User mode. If your Exchange Server 2003 computer has more than 1GB of RAM installed, you need to configure the boot.ini file so that it has 3GB of User mode space available thus, taking advantage of the additional RAM installed above 1GB.
