VALID_FOR : ALL_LOGFILES,ALL_ROLES is not recommended setting for a logical standby for any destination.Because a logical standby is an open
database that is creating its own redo, there is a real possibility of having the log files overwrite each other.This gives you a system that is
unrecoverabl and/or unable to keep synchronized with the primary database.

There is only one invalid combination: STANDBY_LOGFILE,PRIMARY_ROLE.
SELECT dest_id,valid_type,valid_role,valid_now from v$archive_dest;

select * from v$standby_log;
select * from v$logfile where type='STANDBY';

Although standby redo logs are used only when the database is operating in the standby role,you should create standby redo logs on the primary
database so that switching roles does not require additional DBA intervention.

You can maintain the standby database in one of the following modes:
For physical standby databases
1,Redo Apply
2,Open read-only mode
For Logical standby databases
Open read/write mode

Data Guard Broker:Requirments
1,Enterprise Edition of Oracle Databae 10g
2,LOCAL_LISTERNER on each instance must resolve to an address that is reachable by all members
3,GLOABL_DBNAME attribute must be set to a concatenation of: db_unique_name_DGMGRL.db_domain

The Data Guard monitor comprises two components: the DMON process and the configuration file.
Data Guard configuration file:
1,default names are dr1.dat and dr2.dat
2,default location for unix and linux:$ORACLE_HOME/dbs. for windows:ORACLE_HOME\database

startup mount;
alter database force logging; The default value is No.

ARCHIVE_LAG_TARGET: It defines the mean time to failover in the event your primary database fails and you must fail over to the standby.
It likes the parameter of "fast_start_mttr_target" mttr:mean time to recovery target

The standby_archive_dest initialization parameter overrides the directory locaition that is specified with the LOG_ARCHVIE_DEST_n parameter
if both the parameters are specified. So you should set standby_archive_dest to the same location as the local archvive destination for the
physical standby database so that all necessary archvied redo log files for the standby database are in the same location.

Defining the Redo Transport Mode
Use the attributes of LOG_ARCHIVE_DEST_n
1,ARCH and LGWR
2,SYNC and ASYNC(LGWR only)
3,AFFIRM and NOAFFIRM
(primary)(修改成MAXIMUM PROTECTION)
SQL> alter system set log_archive_dest_2='SERVICE=orcldg LGWR SYNC AFFIRM VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=orcldg NODELAY MAX_CONNECTIONS=2 REOPEN=300 NOMAX_FAILURE';

(standby)
SQL> alter system set log_archive_dest_2='SERVICE=orclpri LGWR SYNC AFFIRM VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=orcl NODELAY MAX_CONNECTIONS=2 REOPEN=300 NOMAX_FAILURE';