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## 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 DBVMs, 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?

Prior to Oracle Database Appliance release 19.23, the DB system supported one database per DB system. Starting with Oracle Database Appliance release 19.23, a DB system can run multiple databases.

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 DB system shape decides the cores a DB system can utilize. For example, a DB system with dbsX shape uses X CPU cores, with default memory set to 8 times of CPU core X. You can customize the memory used by the DB system by specifying the memory size at the time of DB system creation, either in the JSON file or in the BUI. Starting Oracle Database Appliance release 19.29, you can scale up and scale down the CPU cores for a DB system using the `odacli modify-dbsystem --core` command.

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 pages, and the DB system is configured using huge pages. So the total memory used by the DB system must be less than the huge pages allocated at the host. If there are databases and application VMs running on the host, then you must also consider them when you plan for CPU and memory resource for DB systems. It is recommended that you reserve at least 2 CPU cores and 24 GB regular memory for the bare metal system host, that is, hypervisor. Check /proc/meminfo for memory allocation details. Use the `odacli modify-osconfigurations` command to update the Huge Pages.

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. Starting with Oracle Database Appliance release 19.24, you can use the `odacli modify-dbsystem` command to attach a vdisk to a DB system. Then, use the vdisk to manually create new file system mount point in the DB system.

The DB system fails to be created due to lack of memory error. But the operating system 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.

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:

- Doc ID 2824390.1: How To Change DBSystem Nodes' Public IP / Network After Deployment on ODA S/M/L Release 19.10 and later at https://support.oracle.com/rs?type=doc&id=2824390.1
- Doc ID 2797758.1: How To Change DBSystem Nodes' Public IP / Network After Deployment on ODA HA Release 19.10 and later at https://support.oracle.com/rs?type=doc&id=2797758.1

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 19.30, you can deploy DB system running Oracle Database Appliance release 19.30. However, you can choose earlier releases of Oracle Grid Infrastructure and Oracle Database, for example, you can deploy Oracle Grid Infrastructure 19.29 and Oracle Database 19.29 on a DB system running Oracle Database Appliance release 19.30. 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. Starting with Oracle Database Appliance release 19.29, you can decrease the DB system memory using the `odacli modify-dbsystem --memory` command. This option does not change the configuration of the database. Make sure configuration of the database is updated first before decreasing the memory of the DB system; otherwise, databases may fail to start after you decrease 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?

Prior to Oracle Database Appliance release 19.23, modifying 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. Starting ith Oracle Database Appliance release 19.23, one DB system supports running multiple databases. Changing the DB system shape using the `odacli modify-dbsystem -s` command does not change the databases in the DB system anymore.

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

On Oracle Database Appliance releases earlier than 19.29, you can use `odacli modify-dbsystem -s` to revert the changes. For example, if you updated the DB system from the default dbs4/32G to dbs4/48G, and you want to revert it to dbs4/32G, you can modify the shape from dbs4 to dbs2, and then from dbs2 to dbs4 again. Starting with Oracle Database Appliance release 19.29, decreasing memory of the DB system is supported using the `odacli modify-dbsystem -m` command. Make sure you reduce the memory used by the database first, before decreasing the DB system memory to avoid database startup failure.

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 security feature is implemented by default.

Parent topic: Oracle Database Appliance Frequently Asked Questions