Data Protection Mode:
1,Maximum protection
2,Maximum availability
3,Maximum performance

Logical Standby Database features:
alter database guard all|standby|none; The default value is all,which means only the SYS can modify the data.

Preparing to create a logical standby database:
1,check for unsupported data types
2,Be aware of unspported DDL commands
3,Ensure row uniqueness
4,Verify that the primary database is configured for archivelog mode
5,Enable supplemental logging

Unsupported objects:
1,Tables and sequences in the SYS schema
2,Tables using table compression
3,Tables used to support materialized views
4,Global temporary tables
5,Tables with unsupported data types(BFILE,ROWID and UROWID,User-defiened types,object types REFs,Varrays,Nested tables,XMLtype)

Query DBA_LOGSTDBY_UNSUPPORTED on the primary database for tables with unsupported data types:
Query DBA_LOGSTDB_NOT_UNIQUE on the primary database to find tables without a unique identifier.
Add a primary key or unique index to ensure that SQL apply can efficiently apply data updates.

Preparing to create a logical standby database.Be sure to check that the initialization parameters have the following values:
PARALLEL_MAX_SERVERS>5
LOG_PARALLELISM=1
SHARED_POOL_SIZE:160M or higher(recommended)

Creating a logical Standby database:
1,create a physical standby database
2,stop redo apply on the physical standby database
3,prepare the primary database to support a logical standby database
4,Build a logMiner Dictionary in the redo data
5,convert to a logical standby database
6,open the logical standby database
7,Verify that the logical standby database is performing properly.

Fast-start failover can be enabled for automatic failover

select thread#,low_sequence#,high_sequence# from v$archive_gap;
alter database register physical logfile 'filespec1';