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: 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 |