2 Simply issuing a commit command when no object change occurred will not trigger the log writer to write. This is easy to test. Create a tight PL/SQL loop containing two lines: a commit and a 1-second sleep. Let this run while operating system tracing the log writer background process. You will not see the log writer issue a write request. However, if you add a third line into the tight PL/SQL loop that performs some type of subsecond DML loop, after 60 seconds, you will see the log writer issue about 60 write calls.

3 Details about these experiments are documented in an OraPub technical paper. Search for "global temp" on the OraPub web site.

4 In a Real Application Clusters (RAC) environment, the lock manager server (LMS) background process can post the log writer background process to write. When an exclusive current (XCUR) model buffer is transferred to another Oracle instance, the holding instance must complete the pending redo associated with the buffer, and the LMS is the process responsible for shipping the buffer to the other instance. During this transfer time, the LMS background process will post the wait event log file sync. Sometimes, the log writer background process will also flush consistent read (CR) buffers in an RAC envirionment. This activity can be monitered via the instance statistic views (for example, v$sysstat) statistic gc cr block flush time.