When running Oracle 10g dataguard, we may find the ORA-00322 error appeared in alert log file from time to time.
This error is caused by the Oracle Bug 5238386 - ORA-322 possible reading standby redo log header and the problem will not hinder the functions of Oracle as long as it does not occur too frequently.

Errors in file /u01/app/oracle/admin/ORCLSB/bdump/orcsb_mrp0_17795.trc:
ORA-00322: log 6 of thread 1 is not current copy
ORA-00312: online log 6 thread 1: '/u03/oradata/ORCLSB/redo01d.log'
ORA-00322: log 6 of thread 1 is not current copy
ORA-00312: online log 6 thread 1: '/u02/oradata/ORCLSB/redo01c.log'
Mon May 14 11:27:15 2009
Errors in file /u01/app/oracle/admin/ORCLSB/bdump/orcsb_mrp0_17795.trc:
ORA-00322: log 6 of thread 1 is not current copy
ORA-00312: online log 6 thread 1: '/u03/oradata/ORCLSB/redo01d.log'
ORA-00322: log 6 of thread 1 is not current copy
ORA-00312: online log 6 thread 1: '/u02/oradata/ORCLSB/redo01c.log'
Mon May 14 11:27:20 2009

However, if the Oracle appears to be unable to apply log in the standby database due to ORA-00322 error. You may consdier to fix the problem
by using one of the following methods

Fix
----
1. Apply the fix for the Bug 5238386.
2. Upgrade the database to the version 10.2.0.4 where the issue has already been fixed.
3. Drop the log group and recreate one
alter database recover managed standby database CANCEL;
alter database drop logfile group 6;
alter database add standby logfile group 6
('/u02/oradata/ORCLSB/redo01c.log',
'/u03/oradata/ORCLSB/redo01d.log') size 100m

References
-----------
Note 294431.1 : ORA-00322 seen in standby alert log when creating a archive log file using SRL.