Opening tables
Distinguishes files, aliases, workareas and RDDs.
Overview
Opening a table binds a data source to a workarea identified by an alias. The alias differs from the physical filename; the RDD determines access behavior. DBUseArea can open a new area and specify driver, source, alias, sharing and read-only modes. A first argument of .F. or Nil may close the current area table; use .T. and a unique alias for an independent opening. File paths resolve on the server, not the SmartClient computer. The Framework index named Abertura de Tabelas lists OpenSm0/OpenSM0Excl rather than the generic DBUseArea contract. (Refs. 1–2)
Commented example
#Include "Protheus.ch"
User Function EdAbre(cFile)
Local aArea := GetArea()
Local cAlias := GetNextAlias()
// Receive an authorized path to a test DBF on the server.
If ValType(cFile) <> "C"
Return .F.
EndIf
If Empty(cFile)
Return .F.
EndIf
DBUseArea(.T., "DBFCDX", cFile, cAlias, .T., .T.)
// Close only the workarea owned by this function.
If Select(cAlias) > 0
(cAlias)->(DbCloseArea())
EndIf
RestArea(aArea)
Return .T.Demonstrates shared, read-only opening followed by owned-area closing on the normal path. File, driver and permission exceptions are not handled; wrapper .T. is not error diagnostics. Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.
- Do not reopen or close caller-owned aliases. Shared access may still fail when another process holds exclusive access. Production code must guarantee cleanup and restoration on error paths too.
- Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.
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