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## Application KVMs on Oracle Database Appliance

FAQs on Application KVMs on Oracle Database Appliance.

The Browser User Interface (BUI) prompts to enter `VM Disk` and `Virtual Disk` when creating VM compute instance. What are `VM Disk` and `Virtual Disk`?

The `VM Disk` is the disk created internally where the VM operating system is installed and shows up as root partition inside the VM. When a VM is created, the `Virtual Disk` is a separate disk that can be used to provide additional space in the VM. The `Virtual Disk` details can be specified when creating the VM, or attached to the existing VM. It can then be formatted to a file system and mounted to a mount point, such as `/data`, inside the VM.

Does Oracle Database Appliance support creation of Oracle Database on application VMs using the vdisk as storage?

Yes. Oracle Database Appliance supports creation of single-instance database using vdisks on application VMs, but you cannot create Oracle RAC databases using vdisks as shared storage on application VMs.

How do I backup and restore the application VMs?

See My Oracle Support note 2779329.1 Backup of KVM guests on ODA 19.9 BM and later.

Does Oracle Database Appliance application KVM support Oracle Solaris 11.4?

Yes. Oracle Solaris 11.4 is included in the list of supported operating systems for Oracle Linux KVM.

What are the options for My Oracle Support for Oracle Solaris 11.4 running on Oracle Database Appliance application KVM?

Support for Oracle Solaris 11.4 is included in Oracle Premier Support for Systems with Oracle Database Appliance.

What are the guidelines for running Oracle Solaris 11.4 on Oracle Database Appliance application KVM?

Oracle Database Appliance does not provide application KVM management. However, for any issues that arise, you can contact My Oracle Support and provide details of the error by reproducing it in a bare metal system environment. For more information, see My Oracle Support Note: Oracle Solaris Support on Virtualization Platforms (Doc ID 1681652.1) at https://support.oracle.com/rs?type=doc&id=1681652.1.

What is the maximum size of RAM for an application VM?

The maximum size depends on the available memory of the Oracle Database Appliance host. It can be as much as the available regular memory and does not include the huge page memory.

How do I attach a new network to the application VM?

When an application VM is created, a default network interface is created in the VM. This interface is attached to the default KVM bridge (virbr0) at the host. This interface is intended for convenient communication between the host and VM. This interface does not attach to any physical network interface on the host. Do not configure this interface to use for any external communication. You should create a vnetwork using the command `odacli create-vnetwork` and attach the vnetwork using the command `odacli modify-vm -avn` to the VM. This creates a second interface in the VM. Configure this network interface for your network requirement. The network interface name in the VM depends on the operating system.

How do I configure Highly-Available NFS (HANFS) on Oracle Database Appliance KVM system?

Oracle Database Appliance KVM uses a different architecture than the Oracle Database Appliance OVM system. There is no ODA_BASE in the Oracle Database Appliance KVM system. The Oracle Grid Infrastructure and Oracle ASM run on the Oracle Database Appliance host where the application VMs and DB systems run. If you want to use Oracle ACFS for storage, then configure HANFS using Oracle ACFS and mount it on the DB system and application VM. See the Oracle ASM Administrator's Guide at the location: https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/understand-acfs-admin.html.

Also, see https://www.oracle.com/technetwork/database/database-technologies/cloud-storage/acfs/learnmore/acfs-nas-max-wp-3618364.html for configuring HANFS. Choose the VIP from the public network used by the DB system or the application VM.

What happens to the KVMs the DB system and the application VM when one of the Oracle Database Appliance high-availability node fails?

Autostart and failover can be set for application VMs as required to enable the failover. Oracle RAC One Node database or Standard Edition High Availability databases on DB systems can failover to the second node automatically.

In case of disaster, if reimaging is only option to recover the Oracle Database Appliance, what are all the backups required to restore all the KVMs on Oracle Database Appliance?

DB systems cannot be restored in such a case and they need to be recreated. The database can be restore from backup once the DB system is recreated. Remote DB backup is essential to recover the database. KVM guest backups are required to restore application VMs.

How can I download the additional RPMS for the application VMs and DB systems?

You manage the application VMs on Oracle Database Appliance, and hence the RPMs in the VM. The policy of updating or installing additional RPMs for DB system is the same as the process on bare metal system. The DB system contains version lock to maintain the integrity of the RPMs. Any RPM that violate the version locks should not be installed or updated. Use the Oracle Database Appliance patch bundle to patch your bare metal and DB systems.

How is memory allocated on Oracle Database Appliance?

After imaging the appliance, about half of the Oracle Database Appliance host memory is allocated to Huge pages pool by default. Huge pages are consumed by the SGA of the databases and DB systems. The remaining memory is shared by the database and other memory usage, Oracle Clusterware such as Oracle Grid Infrastructure and Oracle ASM, application VMs, operating system, swap space, and other applications that you may have installed. Therefore, when sizing the database, DB system, or the application VMs, the huge page and the remaining regular memory must be carefully considered. If Oracle Database Appliance is dedicated to run application VMs, that is, there are no databases on the bare metal system or DB systems, then it is recommended that you reset the HugePages to zero using the odacli modify-osconfigurations -nhp command to release the memory configured as hugeHugePagespage back to the regular memory pool.

How can I create the VM using the KVM template published by Oracle?

See My Oracle Support note Doc ID 2992638.1: Create Apps VM using Oracle Linux template on ODA at

https://support.oracle.com/rs?type=doc&id=2992638.1

How do I configure the application VM network after attaching a vnetwork?

See the Oracle Database Appliance Deployment and User's Guide for your hardware model.

How do I create a Microsoft Windows application VM?

See My Oracle Support Note 2748946.1 at:

https://support.oracle.com/rs?type=doc&id=2748946.1

How do I migrate OVM guest machines from Oracle Database Appliance Virtualized Platform to KVM on bare metal systems?

Starting with Oracle Database Appliance release 19.15, you can use ODACLI commands to perform in-place migration from OVM to KVM on the same Oracle Database Appliance system.

To migrate OVM guest machine to KVM on a different Oracle Database Appliance system, see My Oracle Support Note 2773840.1: Migrating OVM guests from ODA VP to KVM on ODA BM at:

https://support.oracle.com/rs?type=doc&id=2773840.1

Which are the guest operating systems supported on Oracle Database Appliance application VMs?

Oracle Database Appliance application VMs support the same guest operating systems as Oracle KVM. For more information about supported operating systems, see the Oracle Linux KVM User’s Guide.

Why does the command `odacli modify-vm --enable-numa` fail on my application with the error `Cannot get NUMA configuration for odd number of max cores`?

--enable-numa is only supported for application VMs with even number of cpu cores (one cpucore is 2 vcpus). When enabling NUMA for existing application VMs, cpupcores are evenly distributed across two NUMA nodes, that's why it requires VM to have even number of cpucores in order to enable NUMA.

Is overcommitting of CPU and memory supported on application VMs?

Overcommitting of CPU and memory is possible on Oracle KVM. Oracle Database Appliance does not restrict overcommitting of CPU or memory for application VMs. In general, it is not recommended to overcommit CPU or memory. Overcommitting CPU can lead to slow performance of the VMs and the host. Overcommitting memory can cause the system to run out of memory (OOM), which may lead to the Linux kernel shutting down important system processes. If you decide to overcommit CPU or memory, ensure that sufficient testing is performed.

What is the maximum number of application VMs that can be created on Oracle Database Appliance?

The maximum number of application VMs that can be created on Oracle Database Appliance depends on the available CPU and regular memory and whether you want to overcommit CPU and memory. It is recommended that you reserve at least 2 CPU cores and 24 GB memory for the bare metal host (hypervisor). A portion of the Oracle Database Appliance memory is also allocated to HugePages and is not accounted in the regular memory available to the application VMs. Check `/proc/meminfo` for memory allocation details.

Parent topic: Oracle Database Appliance Frequently Asked Questions