Each MIDP-compliant device maintains a dedicated area of device memory for persistent application data storage. MIDlet data stored here persists across multiple invocations of the applications that use it. Both the physical location and the size of the data store are device dependent.

The RMS API abstracts the device-dependent details of the storage area and access to those details, and it provides a uniform mechanism to create, destroy, and modify data. This ensures portability of MIDlets to different devices.

RMS Data Storage Model

The RMS supports the creation and management of multiple record stores, shown in Figure below. A record store is a database whose central abstraction is the record. Each record store consists of zero or more records. A record store name is case sensitive and can consist of a maximum of 32 Unicode characters. A record store is created by a MIDlet.

MIDlets within the same MIDlet suite can share one another's record stores. A MIDlet suite defines a name space for record stores; a record store must have a unique name within a MIDlet suite. The same name can be used in different MIDlet suites, however.

MIDlets can list the names of all the record stores available to them. They can also determine the amount of free space available for storing data. Incidentally, you should be aware that when all MIDlets in a MIDlet suite are removed from a device, the device AMS removes all record stores in the MIDlet suite namespace. All persistent data will be lost. For this reason, you should consider designing applications to include a warning or confirmation that requires users to acknowledge that they understand the potential loss of data when they remove applications. Applications might also include a mechanism to back up the records in a data store to another location. This might require server side support.

The RMS defines the following conceptual operations on an individual record store:

• Add a record.
• Delete a record.
• Change a record.
• Look up (retrieve) a record.
• Enumerate all records.

Records are uniquely identified by a record ID, which is the only primary key type supported. The type of all record ids is the Java built-in type int. The RMS has no support for features—such as tables, rows, columns, data types, and so forth—that are present in relational databases.
 
Records
A record is a byte array of type byte []. The RMS doesn't support the definition or formatting of fields within a record. Your application must define the data elements within a record and their format.

The reader of a record, therefore, must be aware of the format that was used to write the record. Because a record is simply a byte array, applications must convert data from arbitrary types to bytes when writing records, and they must convert from bytes to those types upon reading the data.
 

2007-09-17

Comments(10)

1.	Just what i was looking for. tku. By: Chow Lim at 2008-03-21 01:46:52
2.	rms programe By: hardik at 2008-03-28 23:06:58
3.	Hi hardik, RMS sample program is available at RMS Sample Program By: Daniel Malcolm at 2008-03-29 19:46:18
4.	If i delete a record, will that recId be replaced by next one. more clearly, if the user deletes 3rd record from RMS, will the fourth one come & occupy position 3? By: faisal at 2009-06-08 21:36:29
5.	I will try By: bridges at 2009-09-06 22:09:46
6.	can you give me tutorial how to copy phonebook to RMS???please :) By: rico at 2010-04-04 21:07:57
7.	I want to enter data from a textbox to recordstore and print it again on the emulator screen Please help me.Can anybody provide the revelant code By: Rahul Maurya at 2010-04-10 01:04:51
8.	hie can u plz tell how i maintain my rms for storing my incoming message in milet suite???itz urgent..........reply me on diyagupta66@gmail.com By: diya at 2010-04-30 01:38:06
9.	i will make to try for rms :) By: sebo at 2010-05-20 07:38:28
10.	very brief and easy to understand description of RMS By: moona at 2010-05-26 22:49:26

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