Format options available on 9i:
%s – log sequence number
%S – log sequence number, zero filled
%t – thread number, needed when running RAC as each node creates it』s own archivelog
%T thread number, zero filled, needed when running RAC as each node creates it』s own archivelog
Format options available on 10g
%s – log sequence number
%S – log sequence number, zero filled
%t – thread number, needed when running RAC as each node creates it』s own archivelog
%T – thread number, zero filled, needed when running RAC as each node creates it』s own archivelog
%a – activation ID
%d – database ID
%r – resetlogs ID that ensures unique names are constructed for the archived log files across multiple incarnations of the database.
In 10g, %s, %t, %r are required to be present in the parameter, if it doesn』t the database fail to start with the error ORA-19905: log_archive_format must contain %s, %t and %r. Using this format makes it the archive log filename unique for that instance.
