The log level is simply a database parameter and can easily be changed, look at this page to figure out what level you want. I figured 79 would be a good starting point (64+8+4+2+1). Databases running dataguard should probably have 207 (add 128) to include FAL service details.
How to set the trace level:
[oracle@vm-rac1 ~]$ rsqlplus "/ as sysdba"
SQL*Plus: Release 11.1.0.6.0 - Production on Sun Aug 19 02:35:23 2007
Copyright (c) 1982, 2007, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> show parameter log_archive_trace
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_trace integer 0
SQL> alter system set log_archive_trace=79;
System altered.
SQL> alter system switch logfile;
System altered.
SQL> Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@vm-rac1 ~]$ talert # my shell alias to tail the current alert log
Current log# 1 seq# 7 mem# 0: /u01/app/oracle/oradata/test11g/redo01.log
Sun Aug 19 02:03:14 2007
ARC3: Evaluating archive log 3 thread 1 sequence 6
ARC3: Beginning to archive thread 1 sequence 6 (627362-628594) (test11g)
ARC3: Creating local archive destination LOG_ARCHIVE_DEST_10:
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_%u_.arc' (thread 1 sequence 6)
(test11g)
ARC3: Creating local archive destination LOG_ARCHIVE_DEST_1:
'/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf' (thread 1 sequence 6)
(test11g)
ARC3: Closing local archive destination LOG_ARCHIVE_DEST_10:
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_3dh5pld1_.arc'
(test11g)
Committing creation of archivelog
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_3dh5pld1_.arc'
ARC3: Closing local archive destination LOG_ARCHIVE_DEST_1:
'/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf'
(test11g)
Committing creation of archivelog '/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf'
ARC3: Completed archiving thread 1 sequence 6 (627362-628594) (test11g)
Read details about the log trace level here and general alert log related stuff here.