Cache API in eXtreme Scale

The Cache API behaves as described in the JCache API. Because the specification does not mandate rules on how a near cache must operate, this topic describes how each Cache method affects a near cache. You can configure any cache that has a locking strategy of OPTIMISTIC or NONE to have a near cache.

In this table, X represents the key. A is the near cache value that is associated with the key. B is the far cache value that is associated with the key. C is the new value that is put into the cache. Each row is a cache method. Each column shows the value of the entry in both near and far caches. For a specific cache method, find the column that has your near and far values to learn the return value and behavior. For example, for the getAndPut(X,C) method, if near=null and far=B, the method returns B and sets near and far to C.

Table 1. Behavior of cache methods as to near and far caches. For a cache method with `X` and possibly `A`, `B`, or `C` parameter values, the table provides the return value and behavior.
Cache method	If `near=A` and `far=B`	If `near=null` and `far=B`	If `near=A` and `far=null`
`getAndPut(X,C)`	Return `A`. `near=far=C`	Return `B`. `near=far=C`	Return `A`. `near=far=C`
`getAndRemove(X)`	Return `A`. `near=far=null`	Return `B`. `near=far=null`	Return `A`. `near=far=null`
`getAndReplace(X,C)`	Return `A`. `near=far=C`	Return `B`. `near=far=C`	Return `null`. `near=far=null`
`putIfAbsent(X,C)`	Return `false`. Do nothing.	Return `false`. Do nothing.	Return `true`. `near=far=C`
`remove(X)`	Return `true`. `near=far=null`	Return `true`. `near=far=null`	Return `false`. `near=far=null`
`remove(X,A)`	Return `false`. Do nothing.	Return `false`. Do nothing.	Return `false`. `near=far=null`
`remove(X,B)`	Return `true`. `near=far=null`	Return `true`. `near=far=null`	Return `false`. `near=far=null`
`replace(X,C)`	Return `true`. `near=far=C`	Return `true`. `near=far=C`	Return `false`. `near=far=null`
`replace(X,C,A)`	Return `false`. Do nothing.	Return `false`. Do nothing.	Return `false`. `near=far=null`
`replace(X,C,B)`	Return `true`. `near=far=C`	Return `true`. `near=far=C`	Return `false`. `near=far=null`