1. Frequently Asked Questions
  2. Oracle Database Appliance Frequently Asked Questions
  3. Oracle Database Appliance DB Systems

Oracle Database Appliance DB Systems

FAQs on Oracle Database Appliance DB Systems.

Can I create a single DBVM on a high-availability system?

For single-node systems, each DB system consists of only one DBVM. For high-availability systems, each DB system has two DBVM clusters, one on each Oracle Database Appliance system. Creation of a DB system with only one VM on a high-availability system is not supported.

How many databases does a DB System support?

One database per DB system. The database can be a multitenant container database (CDB) or a non-CDB. If you want to deploy multiple databases on each DB system, it is recommended that you consolidate into a CDB.

Can you run both Oracle Database Standard Edition and Enterprise Edition databases in KVMs on a single Oracle Database Appliance system?

Yes.

What is the CPU cores granularity for DBVM, that is, what is the smallest virtual DB system?

The minimal CPU cores a DB System supports is 2 cores.

Is it supported to run both bare metal databases and KVM DB system on an Oracle Database Appliance system?

Yes. Both bare metal databases and KVM DB system are supported on a single Oracle Database Appliance system.

Is Oracle Database Standard Edition2 licensing of one socket is possible?

In Oracle Database Appliance releases 19.10 and 19.11, you cannot choose from which socket the CPU is allocated. But based on how CPU is allocated, it is possible to use odacli create-cpupool to temporarily occupy the CPU pool on one socket, then create the DB system that uses the CPU pool on the second socket. Starting from release 19.12, you can specify the socket from which the CPU is allocated with the odacli create-cpupool --socket option. This is intended to support SE2 licensing. For other use cases, do not specify the --socket option and allow the system to handle the default CPU allocation. Do not create the CPU pool using mixed options, that is, some CPU pool created with the --socket option, and some created without. This causes imbalanced CPU allocations across the socket and do not optimize CPUs.

How many cores does a DB system utilize?

The shape of the DB system is derived from the shape you select for the database. The CPU cores for the database system is set as one defined in the database shape. For example, if you select odb4 as the database shape, in which the database uses 4 cores, then the database system is created with 4 cores.

Can I use Oracle ACFS inside the DB system?

Oracle ACFS is not supported in the DB system.

Does DB system support oversubscription?

Each DB system is associated with a CPU pool created internally. In release 19.10, the CPU pool associated with a DB system cannot be shared. Starting with release 19.11, you can create the DB system type of CPU pool and share the CPU pool with multiple DB systems. Oversubscribing the CPU pool is allowed among DB systems. Oversubscribing the CPU pool may impact the performance. You must evaluate the impact before implementing CPU pool oversubscription in production.

What are the supported database versions on DB systems?

You can check the supported database version for a DB system version using the command odacli describe-dbsystem-image.

Can I install a later version of the database on the DB system than the Oracle Grid Infrastructure version on the bare metal system?

Yes, starting with release 19.12, DB system supports Oracle Database 21c. You can install Oracle Database 21.3 database in the DB system while the bare metal system runs Oracle Grid Infrastructure 19.x. Run the command odacli describe-dbsystem-image to confirm the Oracle Database and Oracle Grid Infrastructure versions supported on the DB system.

What is the maximum number of DB systems that can be created on an Oracle Database Appliance system?

The maximum number of DB systems depend on the CPU and the memory. By default, half of the host memory is allocated to the huge page, and the DB system is configured using huge page. So the total memory used by the DB system must be less than the huge page allocated at the host. If there are databases and blackbox VMs running at the host, then you must also consider them when you plan for CPU and memory resource for DB systems.

What is the storage used by the DB system?

The DB system local file system includes the /u01, used for Oracle Grid Infrastructure and Oracle Database home, boot partition, the partition for the operating system, swap space, and the /opt partition for the Oracle Database Appliance software. The size of the DB system local file system is fixed at 200 GB per node. For each high-availability system, each DB system node has 200 GB allocated for local storage, and placed on Oracle ACFS on the bare metal system. The databases on the DB system use Oracle ASM disk groups for storage. There is no quota limit per database. The space usage is dependent on how Oracle ASM disk group is used.

The DB system fails to be created due to lack of memory error. But the free space command shows that there is enough memory. What is the cause of the failure?

The DB system uses huge page. By default, Oracle Database Appliance allocates half of the physical memory as huge page. The huge page is shared by the databases on the bare metal system and DB system. Check /proc/meminfo on the bare metal for the number of free huge page available for the DB system. You can increase the huge page configuration based on the usage of the Oracle Database Appliance system.

Can I create multiple DB systems at the same time?

You can create DB systems that use different disk groups for the VM storage at the same time. If they use the same disk group as the VM storage, they must be created in serial.

Can I use FLASH disk group for the DB system VM storage?

Starting with release 19.12, DB systems can be created on FLASH disk group.

Is the name used in DB system case-sensitive or case-insensitive?

The DB system name is case-insensitive. For example, the name DBSystemname1 is considered the same as dbsystemname1.

How can I backup a DB system?

For the detailed procedure, see My Oracle Support Note 2784991.1: Database System backup on Oracle Database Appliance Release 19.10 and later at https://support.oracle.com/rs?type=doc&id=2784991.1.

Why do I need to specify SCAN IP and VIP if I create a single-instance database?

Currently, a DB system with two nodes is created by default on Oracle Database Appliance high-availability environment to support Oracle RAC One node and Standard Edition High Availability databases. Therefore, SCAN IP and VIP are required.

How to resize the root partitions and mount points on DB systems?

The size of the internal file systems on a DB system are optimized and cannot be resized.

Since only one database is supported per DB system, can I create the database as CDB and consolidate databases into different PDBs? Is there any licensing issue?

Only one database is supported per DB system. You can select the CDB option to create a CDB when creating the DB system. One PDB is created by default, and additional PDBs can be created manually by using SQL Plus. You can create a maximum of three PDBs without additional licenses. For more details, see https://blogs.oracle.com/database/post/oracle-database-19c-up-to-3-pdbs-per-cdb-without-licensing-multitenant.

Can I setup the Integrated Data Guard between the bare metal database and DB system database?

Yes, Integrated Oracle Data Guard is supported for DB system in release 19.11 and later. You can set up Oracle Data Guard between bare metal database and DB system database.

Can a different public network be used for the DB system?

Yes. By default, if no public network is provided when creating the DB system, the DB system uses the pubnet from the bare metal as its public network. Starting from release 19.11, you can have different networks for the public network of the DB system. You can create a vnetwork (bridge or bridged-vlan) and select this vnetwork when creating the DB system.

Can I change the DB system memory size without changing number of the CPU?

Yes. You can change the DB system memory size.

Can I detach the default public network from the DB system?

You can select a vnetwork as the public network when creating the DB system. By default, the DB system uses the pubnet as the public network. You cannot detach this public network after the DB system is created because it used by Oracle Grid Infrastructure and the database. You can add a new public network to an existing DB system and detach this second public network with the odacli modify-dbsystem command.

How do I change the public network of a DB system?

Refer to the following My Oracle Support Notes:

Can I create a DB system of an earlier release?

You can only create a DB system of the same release as the bare metal system on Oracle Database Appliance. For example, if the bare metal system is on Oracle Database Appliance release 19.13, you can deploy DB system running Oracle Database Appliance release 19.13. However, you can choose earlier releases of Oracle Grid Infrastructure and Oracle Database, for example, you can deploy Oracle Grid Infrastructure 19.12 and Oracle Database 19.12 on a DB system running Oracle Database Appliance release 19.13. Use the command odacli describe-dbsystem-image to check the supported DB system, Oracle Grid Infrastructure, and Oracle Database releases.

What is the modify dbsystem memory feature?

The modify dbsystem memory feature allows you to increase the DB system memory so that you can add more memory to the database (SGA or PGA). It is recommended that you select DB system shapes instead, optimizing the sizing of CPU and memory used by the database. If you want to increase database memory without changing the number of CPUs, then use the modify dbsystem memory feature.

Why is decreasing the DB system memory not supported? How can I reduce the DB system memory?

Database CPU and memory sizing ratios on Oracle Database Appliance are optimized for pre-defined database shapes. Reducing the database memory for a given CPU setting is against the sizing best practices recommended on Oracle Database Appliance. If reducing database memory is justified, then you can reduce the database memory without modifying the DB system memory. Change the DB system shape to reduce the DB system memory.

If I increase the DB system memory and the database memory and then change the DB system shape by using the command odacli modify-dbsystem -s, what happens to the database memory?

Changing the DB system shape changes the database inside the DB system accordingly. So, both the DB system and the database setting, including memory, are reset to match the new shape of the DB system.

I increased the dbsystem memory. How do I revert the changes?

You can use odacli modify-dbsystem -s to revert the changes. For example, if you updated the DB system from the default odb4/32G to odb4/48G. To revert it to odb4/32G, you can modify the shape from odb4 to odb2, and then from odb2 to odb4 again.

How does Oracle Database Appliance manage the access control to the database on a DB system?

The database on a DB system accesses the Oracle ASM disk groups managed by Oracle ASM. Oracle ASM access control prevents a user of one DB system from accessing files owned by another DB system. For more information, refer to the Managing Oracle ASM File Access Control for Disk Groups topic in the Oracle ASM Administrator's Guide at https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/asm-access-control-diskgroups.html#GUID-89BB888A-BA1C-4095-BB6D-C3BE142CB371. When you create a DB system on Oracle Database Appliance, this this security feature is implemented by default.

Parent topic: Oracle Database Appliance Frequently Asked Questions