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Index

Messaging Server maintains an index entry in memory. A copy of the index entry of all message types is stored in the SQL database, so that it can be restored in the event of a system reset or Messaging 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.

Operating with the SQL database

The SQL database is used to store each TMsvEntry (index entry) as a row of an SQL table in the SQL database. It caches entries, and maintains the most recently accessed entries in the RAM. Entries are cached in the RAM, and are loaded only when required. The RAM usage is controlled by emptying the oldest entry in the cache when it is full. For more information on caching, see Caching. The following illustration shows the architecture of the Message Server with the SQL database.

Figure 1. Message Server architecture with the SQL database

Note: Write operations like updating, creating and deleting entries require disk operation to retrieve TMsvEntry from database, because the entry cache is always in synchronisation with the corresponding entry in the database.

Advantages

The following are the advantages of using the SQL database to store index entries:

Reduces the amount of RAM used by messaging, as the message the index file is not used.
Enables more messages to be stored on the device, as the number of messages stored is not restricted to the amount of RAM available to store the message index file.
Enables controlled usage of RAM, as index entries are loaded on a need basis.
Eliminates the possibility of the message index file getting damaged and messages stored on the device getting deleted.
Provides advanced search and sort capabilities for searching messages.
Accesses and manages message entries on one or more drives at the same time.

Index fields

The following information is stored for each index entry. Some fields only apply to particular types of entry, such as, messages or services; other fields can be interpreted differently for different entry types.

Attachment flag	Indicates that the message has an attachment
BIO	BIO message type
Complete flag	Indicates that the message is complete (for example download has completed.
Connected flag	For a service: indicates whether it is currently connected to a remote server
Deleted flag	Indicates that the entry has been deleted. The entry is not removed until any PC synchronisation tools have been informed of the deletion.
Description	A text string, usually giving the subject of the message
Details	A text string, as follows: Message: For received messages, this is the sender; for outgoing messages, it is the recipient Attachment: The name of the attachment Folder: The name of the folder Service: The name of the service
Error	A system-wide or MTM-specific error code
Flag	Use
Failed flag	For an outgoing message: indicates that sending failed
Identifier	An integer that uniquely identifies the entry in the Index
In preparation	Entry deleted if server restarts
MTM	A unique identifier specifying the MTM associated with the entry
MTM Data	Three integer fields for MTM-specific use
Multiple Recipients flag	Indicates the message has multiple recipients that require separate transmissions (for example, a fax going to two people)
New flag	Indicates a new message in a folder
Owner flag	Indicates that the entry owns other entries (that it is a parent)
Parent	An integer giving the identifier of the entry’s parent
Priority	An integer giving the message priority
Read flag	Indicates that a message has been read
Read Only flag	Indicates that the entry is read-only
Related folder	The identifier of a target folder for copying or moving entries
Sending state	Describes the state the message is in, for example "Sending", "Failed" and "Sent"
Service	The identifier of the service by which the message is to be sent or from which it was received
Size	An integer giving the size of the message
Standard Folder flag	Identifies standard folders so that they can be properly sorted and stops them being changed/deleted
Time	The time when the message was last edited, sent, or received. Includes date.
Type	A unique identifier giving the type (service, folder, message, and attachment) of the entry
Visibility flag	Indicates the intended visibility of the entry to users of message client applications

Parent topic: Storage of Messages