[DataGuard] DG Series

[DataGuard] DG Series

I. New Features of the physical standby Database

1. The physical standby database can be queried in real time.

In the physical standby database before the Oracle 11g, the Standby database can be opened in read-only mode, but the Media Recovery (redo Apply) process stops. If the standby database is in the recovery process, the Standby database cannot be opened. Oracle 11g resolves this conflict and can open the database while restoring it.

2. Speed up backup of the slave Database

The Block Tracking technology was introduced in oracle10g to monitor those databases modified since the last increment. This can speed up Incremental backup, but this function can only be effective on the master database, oracle11g resolves this conflict, and the backup of the slave database also supports Block Tracking, so that you can quickly perform backup on the slave database to reduce the load on the master database.

3. snapshot slave database (oracle10g already exists)

This feature allows the physical standby database to be opened in read/write mode, but does not disrupt its function as the standby database. This feature can be used to perform some tests on the physical standby database, reset the database to a physical standby database. Of course, when the standby database is opened in read/write mode, it can only accept the redo passed by the primary database, but cannot apply the redo. It is actually because the Flashback technology is used on the slave database to implement this function.

4. Improve redo apply performance

Oracle11g can use parallel technology for redo apply to speed up recovery.

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References:

Important configuration parameters of Oracle Data Guard

Configure Oracle 11g Data Guard based on the same host

Explore Oracle 11g elastic uard

Oracle Data Guard (RAC + DG) archive deletion policies and scripts

Role conversion for Oracle Data Guard

FAL gap in Oracle Data Guard logs

Oracle 11g Data Guard Error 16143 Heartbeat failed to connect to standby

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Ii. New Features of the logical standby Database

1. More data types are supported.

XMLType data type (CLOB storage)

2. The following oracle packages and Data Encryption are supported.

DBMS_FGA (Fine Grained Auditing)

DBMS_RLS (Virtual Private Database)

In fact, it supports fine-grained auditing and virtual database functions on the logical standby database.

Support for Transparent Data Encryption (TDE)

The slave Database supports parallel DDL.

3. Fast-Start Failover

You can perform failover more quickly and precisely control the events that trigger the failover. For example, you can issue a failover based on a specific ora error number.

3. Other improvements

1. Redo Compression

This process is a prerequisite for data guard to send archived logs from the master database to the backup database server and then apply them to the database. An important part of the time difference between the master and slave databases is the time when logs are archived. If the redo stream is compressed, this process can be accelerated. In oracle11g, you can use SQL * Net to set the compression parameter to true. This compresses the redo stream transmitted to the slave database server. This process applies to the logs transmitted between Gap Resolution. The following command can be used to enable compression:

SQL> alter system set log_archive_dest_2 = 'service = DG_ORCLSTD LGWR ASYNC valid_for = (ONLINE_LOGFILES, PRIMARY_ROLE) db_unique_name = ORCLSTD compression = enable ';

2. Network timeout

The tool principle of the Data guard environment is to connect to the database instance of the backup database server and send redo Data to the backup database server. If the instance does not respond in time, the log service waits for the specified timeout value and then gives up. You can use the net_timeout parameter in the Oracle database to set the timeout value. In the maximum protection mode, the log transmission service will give up after 20 attempts. First, you must know the current latency in log transmission. The new view v $ redo_dest_resp_histogram represents the time value in the histogram form. This view shows the number of transmission elapsed time in the middle of a given column. If you want to view this view after running for a few days, you can clearly set the timeout time. Run the following command to set the timeout:

SQL> alter system set log_archive_dest_2 = 'service = DG_ORCLSTD LGWR ASYNC valid_for = (ONLINE_LOGFILES, PRIMARY_ROLE) db_unique_name = ORCLSTD compression = enable net_timeout = 20 ';

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