Symbian
Symbian OS Library

SYMBIAN OS V9.3

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Storage

The data for the items in the messaging system — attachments, folders, and message services as well as messages — can be stored in three places:

Some entry types do not usually have associated message stores or binary files: for example, folders, being simple, can be wholly described by an index entry.


Index

As the Message Server is expected to run continuously, it maintains the index in memory. A copy of the index is persisted in the file system, so that it can be restored in the event of a system reset or Message Server failure.

Some fields only apply to particular types of entry (such as messages or services); other fields can be interpreted differently for different entry types.

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Message store

A message store contains message data in a variable number of streams, each of which is referenced by a unique identifier. This concept is known as a dictionary file store.

MTMs can create additional streams in a message store to hold MTM-specific message data. Usually, at least one stream is devoted to non-generic header information, such as recipient information.

The Message Server allows multiple read-only and a single read/write access to a message store at any one time.

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Binary files

Any entry can have binary files associated with it. These are stored in a directory, created by the Message Server, that is unique to the entry. Before v9.0, clients read and wrote files directly into that directory. From v9.0, clients use the messaging API classes MMsvAttachmentManager and CMsvAttachment to manage attachments.

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Storage abstractions

The abstractions through which applications access the various types of storage are key to Messaging. Briefly: