Slide 10.3: Palm OS databases (cont.)   Slide 10.5: Palm OS databases (cont.)   Home

Palm OS Databases (Cont.)

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Structure of a Database Header (Cont.)

The attribute field, shown on the right, is 8 bits long and contains 4 flags and a 4-bit category number. The category number is used to place records into user-defined categories like “business” or “personal.”

Each record entry has the local ID of the record, 8 attribute bits, and a 3-byte unique ID for the record.

• Local IDs make the database slot-independent. Since all records for a database reside on the same memory card as the header, the handle of any record in the database can be quickly calculated. When an application requests a specific record from a database, the Data Manager returns a handle to the record that it determines from the stored local ID.


• The unique ID must be unique for each record within a database. It remains the same for a particular record no matter how many times the record is modified. It is used during synchronization with the desktop to track records on the Palm Powered handheld with the same records on the desktop system.

When the user deletes or archives a record on Palm OS:

• The delete bit is set in the attributes flags, but its entry in the database header remains until the next synchronization with the PC.


• The dirty bit is set whenever the record is updated.


• The busy bit is set when the record is locked for reading or writing.


• The secret bit is set for records that should not be displayed before the user password has been entered on the handheld.