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C++Builder Database Architecture
The TransIsolation property controls the transaction isolation level (TIL) on the database
server. The TIL on the server controls the accessibility of concurrent transactions to changes
made by one another.
TransIsolation has three possible values: tiDirtyRead, tiReadCommitted, and tiRepeatableRead
(default is tiReadCommited). These TransIsolation values have the following effects:
■ tiDirtyRead—Uncommitted changes by other transactions are visible.
■ tiReadCommitted—Only committed changes by other transactions are visible.
■ tiRepeatableRead—Changes by other transactions to previously read data are not
visible, which means that every time a transaction reads a given record, it always
gets the exact same record.
The StartTransaction method marks the beginning of a group of database changes that you
want to be treated as a unit. They will either all be applied to the database or none of them
will be.
NOTE
Commit makes permanent the database changes that have occurred since the transaction was
started. Think of it as a database save command.
Rollback discards the database changes that have been made since the transaction began.
Think of it as a database undo command.
TTable
You can also control transaction processing on your server using
Passthrough SQL. To do this, you issue SQL commands that change
the transaction processing on your server. Be aware that doing this with
SQLPASSTHRUMODE set to SHARED AUTOCOMMIT or SHARED NOAUTOCOMMIT
could cause your new TIL setting to affect other transactions initiated
by your application.
Module: DBTables Class ancestor: TDBDataSet
TTable is a direct descendant of the TDBDataSet class and an indirect descendant of the
TDataset class. You access database tables using the TTable component. When you open a
TTable, you establish a connection between your application and the table. You add, change,
and delete rows in database tables using the TTable component.
Table 12.8 lists the key properties, Table 12.9 the key methods, and Table 12.10 the key
events of TTable.
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