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How to manage the Coherence Elastic Data use of Flash Journal file space on Disk? (Doc ID 2411335.1)

Last updated on JUNE 30, 2019

Applies to:

Oracle Coherence - Version and later
Information in this document applies to any platform.


The Elastic Data feature is used to seamlessly store data across memory and disk-based devices. This feature is especially tuned to take advantage of fast disk-based devices such as Solid State Disks (SSD) and enables near memory speed while storing and reading data from SSDs. The Elastic Data feature uses a technique called journaling to optimize the storage across memory and disk.

Elastic data contains two distinct components: the RAM journal for storing data in-memory and the flash journal for storing data to disk-based devices. These can be combined in different combinations and are typically used for backing maps and backup storage but can also be used with composite caches (for example, a near cache). The RAM journal can work with the flash journal to enable seamless overflow to disk.

Similar to a partitioned cache, a federated cache consists of a set of partitions within each cluster. Generally, a federated cache running within a single cluster has functionality identical to a partitioned cache. Each partition has a logical outbound update queue. This queue is fault-tolerant and can survive rebalancing and failover/failback operations.

All of these outbound queues are stored using the Elastic Data feature of Coherence. This feature uses two per-JVM storage buffers — a RamJournal in on-heap RAM and a FlashJournal stored on disk (which may be local or shared, and is expected — but not required — to have performance similar to solid state disk). It is important to remember that Elastic Data is a single resource shared by all services running on the cluster member.

How to manage the Coherence Elastic Data use of Flash Journal file space on Disk?


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