Object Store (Windows CE 5.0)
The object store in Windows CE provides persistent storage for applications and their related data even when the main power supply is lost, provided there is a backup power supply. One or more memory storage chips, which typically are nonvolatile RAM chips, compose the physical object store.
Conceptually, the object store consists of three types of persistent storage:
- File systems
- Databases
- A system registry
Although file systems, databases, and the system registry share a single memory heap, they do not necessarily reside physically in the object store. They can reside in ROM, on separately installed systems, or on an external device, such as a flash memory device. Data is created and retrieved according to the storage type, independent of the actual storage device.
The operating system uses the object store to perform the following tasks:
- Manage the stack and memory heap
- Compress and expand files as necessary
- Seamlessly integrate ROM-based applications and RAM-based data
Storage Mechanism
The storage mechanism for data in the object store is transaction-based. If power is interrupted while data is being written to the object store, Windows CE ensures that the store is not corrupted. It does this by either completing the operation when the system restarts or reverting to the last known good state before the interruption. For system files, including the registry settings, this can mean reloading the initial settings from ROM if you did not define a backup system for saving the current settings.
Size
The maximum size for the RAM file system is 256 MB, with a maximum size of 32 MB for a single file. The maximum number of objects in the object store is approximately 4,000,000.
The maximum file size is 4 GB. A 4-GB file can be achieved through compression and with the object store not assigning memory to unused portions of the file.
See Also
Objects and Object Identifiers | Using Object Identifiers | File Systems and Data Store OS Design Development | Object Store Size
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