Palm OS Programming, 2nd Edition

Overview of Databases and Records

To begin with, don’t get your hopes up when you hear the word database. The Data Manager doesn’t support anything like a desktop database: no fields, no indexing, no select statements. At its heart, a Palm database is just an array of memory chunks.

Once you get past its unusual location, the organization of data and databases on the Palm OS is fairly simple. It’s organized into two components: databases and records. The relationship between the two is straightforward. A database is a related collection of records. Records are relocatable blocks of memory (handles) and an individual record can’t exceed 64 KB in size. A database on the Palm OS consists of an array of record handles. This simplicity is one reason for the very fast performance of the Data Manager.

There are two different types of databases:

Record databases

These are normally used to store application data and are synced by conduits. They are also called PDBs.

Resource databases

These are normally applications, overlays (localized resources), and shared libraries and don’t normally change at runtime. They are also called PRCs.

Let’s look at record databases first. After that, we will turn to resource databases.

Record Databases

A database, as a collection of records, maintains certain key information about each record. This information includes:

• The location of the record.

• A 3-byte unique ID. This ID is unique only within a given database. It is assigned automatically by the Data Manager ...