In OCMAM, map data is stored in an online mutable or protected cache.
The following diagram shows a high-level overview of the OCMAM components.
Figure 1. High-level component view
In the online mutable cache, you can set the maximum storage size and enable the eviction policy. If data reaches the maximum allowed size, it is evicted based on the least-recently-used (LRU) policy. For more information on the eviction configuration, see "Protect tiles from eviction" and "Allow eviction of tiles" in Offline mode.
If you want to use some map regions with all the related data offline and keep a consistent view of them, you can save the catalog that contains these regions to the protected cache.
The protected cache needs to contain the full view of a region at all levels to allow offline usage. If you want to add the same data version to the protected and mutable caches, to omit duplicates and reduce traffic usage, first download regions to the protected cache and only then to the mutable cache. Otherwise, downloaded bundles are duplicated in both caches. For more information on how to work with data in the mutable and protected caches, see Manage data in mutable cache and Manage data in protected cache.
In the table below, find the features that the online mutable and protected cache support.
Feature
Protected cache
Online mutable cache
Map consistency
Yes Prefetched regions are protected from eviction. Therefore, this storage provides a consistent view at all tile levels.
No Only prefetched regions have a consistent view.
Update ways
Storage media, online
Online
Streamable
No
Yes Data can be updated incrementally.
Max storage size is configurable
No
Yes The default value is 32 MB. Data that exceeds the maximum size is evicted.
Map region support
Yes This storage type saves entire regions with all related data.
No
Update based on bounding box
No
Yes
Set up the HERE Data SDK for C++ cache
To set up the SDK cache, use the cache_settings field of the DataStoreServerSettings structure.