Oracle Active Data Guard Features and Benefits

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Oracle Active Data Guard enhances the performance of production databases by offloading resource-consuming operations to one or more standby databases. This protects interactive users and critical business tasks from the impact of long-running operations. 

Active Data Guard enables a physical standby database to be used for real-time reporting with minimal latency. Compared to traditional replication methods, it is simple to use and has very good performance.

Oracle Active Data Guard enables read-only access to a physical standby database for queries, sorting, reporting, web-based access, etc., while continuously applying changes or archived logs received from the production database.

Active Data Guard also enables fast incremental backups when offloading backups to a standby database, and can provide additional benefits of high availability and disaster protection against planned or unplanned outages at the production site.

Features

  • Physical Standby with Real-Time Query
  • Fast Incremental Backup on Physical Standby

Benefits

  • Increase performance– Offload unpredictable workloads to an up-to-date replica of the production database
  • Simplify operations– Eliminate management complexity that accompanies traditional replication solutions
  • Eliminate compromise– The reporting replica is up to date and online at all times, which is not possible with traditional storage mirroring technology
  • Reduce cost– An Oracle Active Data Guard physical standby database can also provide disaster recovery and/or serve as a test database – no additional storage or servers required
  • Enables a standby database for use in real-time for reporting
  • Offloads backup operations
  • Insulates critical operations from unexpected system impacts
  • Provides high availability and disaster protection

Oracle 23ai : The all new Hybrid Read-Only for pluggable databases (PDBs)

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The latest Oracle database version, Oracle 23ai, introduced a new open mode called Hybrid Read-Only for pluggable databases (PDBs). Local users can only connect with read-only access when a PDB is set to this new mode. However, common users are not restricted and can still perform write operations.

Command to convert to this mode

SQL> ALTER PLUGGABLE DATABASE TECHNOPDB OPEN HYBRID READ ONLY;
Pluggable database altered.

SQL> show pdbs;
    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 TECHNOPDB                      READ WRITE NO

Testing Write Access with common user - SYS

Now, we connect to TECHNOPDB as the SYS user and test write operations:

sqlplus "sys/sys@target:1521/TECHNOPDB as sysdba"

SQL> show user;
USER is "SYS"

SQL> select OPEN_MODE from v$pdbs;
OPEN_MODE
----------
READ WRITE

SQL> create table tech_user.test_tab(id number);
Table created.

As we can see, the SYS user sees the OPEN_MODE as READ WRITE, even though the PDB was opened in HYBRID READ ONLY mode.

Testing Write Access as any Local User

Now, let us repeat the test with a local user named VAHID:

sqlplus "tech_local/test123@target:1521/TECHNOPDB"

SQL> show user;
USER is "tech_local"

SQL> select OPEN_MODE from v$pdbs;
OPEN_MODE
----------
READ ONLY

SQL> create table tech_user.test_tab(id number);
ORA-16000: Attempting to modify database or pluggable database that is open for read-only access.

As expected, the local user (TECH_LOCAL) is not allowed to perform write operations.

Checking Hybrid Read-Only Mode Status

The view V$CONTAINER_TOPOLOGY can help to check the HYBRID READ ONLY mode:

SQL> select IS_HYBRID_READ_ONLY, CON_NAME, OPEN_MODE from V$CONTAINER_TOPOLOGY;

IS_HYBRID_READ_ONLY  CON_NAME   OPEN_MODE
-------------------- ---------- ----------
YES                  ORCLORPDB  READ WRITE

 

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