1. Oracle VM Server for SPARC 3.6 Administration Guide
  2. Migrating Domains
  3. Migrating an Active Domain
  4. Migration Requirements for Memory

Migration Requirements for Memory

The target machine memory requirements are as follows:

  • Sufficient free memory to accommodate the migration of a domain

  • The free memory must be available in a compatible layout

Compatibility requirements differ for each SPARC platform, but in all cases Oracle VM Server for SPARC must take into account memory page sizes during a migration operation. In particular, two page sizes are used when laying out the memory of a migrating domain on the target machine:

  • Hardware largest page size – The largest page size that is supported by the hardware platform.

  • Effective largest page size – The largest page size that is available for the domain to use. This page size is always less than or equal to the hardware largest page size.

The real address and physical address alignments are relative to the hardware largest supported page size and must be preserved for each memory block in the migrated domain.

For a guest domain that runs at least the Oracle Solaris 11.3 OS, the migrated domain's memory blocks might be split automatically during the migration so that the migrated domain can fit into smaller available free memory blocks. Memory blocks can only be split on boundaries that are aligned with the effective largest page size.

Other memory layout requirements for operating systems, firmware, or platforms might prevent memory blocks from being split during a given migration. This situation could cause the migration to fail even when the total amount of free memory available is sufficient for the domain.

Use the ldm list-domain -o domain command to determine the hardware largest page size that is supported by the target machine and the effective largest page size that is supported by the domain.

The following example shows the read-only effective-max-pagesize and hardware-max-pagesize property values. The effective-max-pagesize property value is for the ldg1 domain. The hardware-max-pagesize is for the platform. 

primary# prtdiag|head -n 1
System Configuration:  Oracle Corporation  sun4v SPARC T7-2 
primary# ldm list-domain -o domain ldg1 | grep pagesize
effective-max-pagesize=2G
hardware-max-pagesize=16G