Data Access Layer Specifics
The DAL presented here is essentially the same DAL that TMS uses in enterprise applications for its clients. I'll describe the operation of the DAL in detail here, but I'll concentrate only on using a DAL, not on building one. Remember that we want to concentrate on business object development, so this is the data object that our business objects will interface with.
The DAL below consists of only six methods. All other aspects of database operation (for instance, cursor types, locking models, parameter information, and type translation) are encapsulated and managed by the DAL itself.
cDAL Interface
| Member | Description |
| OpenRecordset | Returns a recordset of data |
| UpdateRecordset | Updates a recordset of data |
| ExecuteCommand | Executes a command that doesn't involve a recordset |
| BeginTransaction | Starts a transaction |
| CommitTransaction | Commits a transaction |
| RollbackTransaction | Rolls back a transaction |
What's all this recordset malarkey? Well, this is (surprise, surprise) an abstracted custom recordset (cRecordset). We must investigate this recordset carefully before we look at the operation of the DAL itself.