Resolution:
You cannot control when data will be written to the backing store from a cache, rather you can set how often data will be written using a write-delay value. Moreover, the "write-requeue-threshold" is for failed writes, i.e., it determines the maximum number of entries which can be in memory in case of a database failure. Try changing the value of the following parameters in "coherence-cache-config.xml" as per the number of concept instances in the project.
    
1). The write-requeue-threshold.  
2). The write-delay.              

As per the Tangosol documentation, <write-requeue-threshold>, Tangosol recommends the following approach to set a value for this parameter. "With a 1GB heap, our recommendation is to use at most 3/4 for data storage. Assuming 3MB objects the <write-requeue-threshold> should be 750/3=250."

References :
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More information about these settings can be found at  http://wiki.tangosol.com/display/COH33UG/versioned-backing-map-scheme