Client logs capture data about client application operations for all devices subscribed to a package. You can use the data to track errors and identify performance issues.
By default, logged data includes the user name, device ID, mobile business object with which the client is syncing, the operation the client is performing, the success or failure of the server-side operation, current log level, date and time stamp, the log message associated with the message.
Developers use client-side APIs to enable this capability to log critical application data on the device that can be uploaded automatically to the server where it is visible in the package's client log. The capability can implemented so that enabling and disabling logging does not require any user intervention, is transparent, and can be turned on or off automatically.
See Sybase Control Center > Manage > Managing Unwired Platform > Routine System Maintenance Tasks > Checking Client Application Logs.