Question

What is the Virtual Transaction Log file in SQL Server?

Answer 1

From MSDN:

The SQL Server Database Engine divides
each physical log file internally into
a number of virtual log files. Virtual
log files have no fixed size, and
there is no fixed number of virtual
log files for a physical log file. The
Database Engine chooses the size of
the virtual log files dynamically
while it is creating or extending log
files. The Database Engine tries to
maintain a small number of virtual
files. The size of the virtual files
after a log file has been extended is
the sum of the size of the existing
log and the size of the new file
increment. The size or number of
virtual log files cannot be configured
or set by administrators.

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The transaction log is a wrap-around
file. For example, consider a database
with one physical log file divided
into four virtual log files. When the
database is created, the logical log
file begins at the start of the
physical log file. New log records are
added at the end of the logical log
and expand toward the end of the
physical log. Log truncation frees any
virtual logs whose records all appear
in front of the minimum recovery log
sequence number (MinLSN).

When the end of the logical log
reaches the end of the physical log
file, the new log records wrap around
to the start of the physical log file.