Caching sql query not happening

> Does anyone know why a statement such as:
>
> SELECT ID
> FROM ELSR dups
> WHERE (dups.directoryID = :"SYS_B_0"
> AND dups.DeviceIdentifier = :"SYS_B_1"
> AND dups.serviceStartTime BETWEEN TIMESTAMP:"SYS_B_2" AND
> TIMESTAMP:"SYS_B_3")
>
> will never cache in the Shared Pool?
>
> In other words, even though all of the parameters are bind variables, this
> will always be parsed seperately, and never cache.
>
> Thanks
> Vikas

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