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New optional flag --mode will be added.
Possible values are PERSISTENT, INMEMORY, BOTHALL.
Default value is PERSISTENT to keep existing behaviour of command.
When concurrent creation of in-memory and persistent snapshots will be implemented default value can be changed to BOTH.

Example:

> ./control.sh --snapshot --create SNP --mode INMEMORYALL

Creation

1. PME guarantees to make sure of visibility of all dirty pages:

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• DataRegionConfiguration#persistenceEnabled=false  for in-memory caches by the definition.
• The same value must be for DataRegionConfiguration when cache group restored from in-memory snapshot.
• After this feature implemented PageIO will require to be backward compatible.
• The way to restore snapshot on different topology must be further investigated.
• Empty pages of DataRegion will be written to snapshot.
• Compaction of snapshot must be further investigated.
• No concurrent snapshot operation - persistent, in-memory allowed. This can be eliminated in next phases to provide the ability to create full cluster snapshot by one command.
• In case of mixed cluster(both persistence and in-memory data region exists) metastorage is persistent and must be included into in-memory snapshot.  

Phases scopes

• Phase 1
  • snapshot creation.
  • restore snapshot on the same topology.
  • control utility integration.
• Phase 2
  • restore snapshot on different topology.
• Phase 3
  • snapshot compactification.

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