BigMemory Max 4.3.5 | Product Documentation | BigMemory Max Administrator Guide | Managing Near-Memory-Full Conditions | Behavior of the TSA under Near-Memory-Full Conditions
 
Behavior of the TSA under Near-Memory-Full Conditions
In a near-memory-full condition, where evictions are not happening fast enough to keep the data set within its BigMemory size limitations, the TSA will put a throttle on operations for a temporary period while it attempts to automatically recover in the background. If unable to recover, the TSA will move into "restricted mode" to prevent out-of-memory errors. The Terracotta Management Console (TMC) uses events to report when the TSA enters restricted mode and allows you to execute additional recovery measures. See Monitoring Cluster Events.
Summary of TSA behavior in near-memory-full conditions:
*If usage reaches its critical threshold, T1, then it enters "throttle mode," where writes are slowed while the TSA attempts to evict eligible cache entries in order to bring memory usage within the configured range.
*If usage reaches its halt threshold, T2, then it enters "restricted mode," where writes are blocked, an exception is thrown, and operator intervention is needed to reduce memory usage.
*When usage falls below T1, then the TSA returns to normal operation.
Throttle mode
Restricted mode
Entered when
Disk, dataStorage , and/or offheap usage crosses its critical threshold
Disk, dataStorage , and/or offheap usage crosses its halt threshold
Operator event
"TPS seems really low; marking us as being throttled'
"We're in restricted mode; waiting a while and retrying"
Data access
Modifications to in-memory data are slowed
Modifications to in-memory data are blocked
Allowed operations
All cache operations still allowed
Only gets, removes, and config changes are allowed
Actions
Evictions continue automatically in the background
Operator intervention required to make additional evictions
State of the data
Evictable data is still present
No more data present in memory that can be evicted by the evictor (all caches are pinned)
Recovery
Automatic
From the TMC or programmatically, clear caches and/or remove entries from a data set
Back to normal operation
As soon as the background evictions have time to catch up and reduce the data set to within its limitations
After user intervention clears space, the TSA will automatically continue with normal operation
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