XFA Specification
Chapter 20, Source Set Specification
Source Set Element Reference
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The lockType property
Controls what type of lock to apply against other users and/or processors. The text within quotation marks
below is taken from the section "Types of Locks" in Chapter 8 of the ADO Programmer's Guide [ADO].
readOnly
"Indicates read-only records. You cannot alter the data. A read-only lock is the 'fastest' type of lock
because it does not require the server to maintain a lock on the records."
unspecified
"Does not specify a type of lock." The lock type is determined by the database and/or XFA
application. XFA does not provide a way to find out what type of lock was chosen, so the form
creator must make pessimistic assumptions.
pessimistic
"Indicates pessimistic locking, record by record. The provider does what is necessary to ensure
successful editing of the records, usually by locking records at the data source immediately before
editing. Of course, this means that the records are unavailable to other users once you begin to
edit, until you release the lock by calling Update. Use this type of lock in a system where you
cannot afford to have concurrent changes to data, such as in a reservation system."
optimistic
"Indicates that the provider uses optimistic locking - locking records only when you call the
Update method. This means that there is a chance that the data may be changed by another user
between the time you edit the record and when you call Update, which creates conflicts. Use this
lock type in situations where the chances of a collision are low or where collisions can be readily
resolved."
batchOptimistic
"Indicates optimistic batch updates. Required for batch update mode.
Many applications fetch a number of rows at once and then need to make coordinated updates
that include the entire set of rows to be inserted, updated, or deleted. With batch cursors, only one
round trip to the server is needed, thus improving update performance and decreasing network
traffic. Using a batch cursor library, you can create a static cursor and then disconnect from the
data source. At this point you can make changes to the rows and subsequently reconnect and
post the changes to the data source in a batch." XFA does not provide a way to control
disconnecting and reconnecting. Whether or not this optimization is performed is
implementation-defined.
The max property
The maximum number of records to return. This corresponds to the "MaxRecords" property of the
Recordset ADO object. The value of this attribute must be a non-negative integer.
The special value 0 means there is no limit. This is the default.
The name property
An identifier that may be used to identify this element in script expressions.
The use property
Invokes another object in the same document as a prototype for this object. The content of this property is
either a SOM expression (which cannot start with '#') or a '#' character followed by an XML ID.