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If you need to read rows before finding the one to modify, don't lock until you find the row you want, but read again after you lock it.
See also
Remarks
Lock alerts the network system that the program wishes to establish a lock on a table or row. If the program attempts to set a lock that has been previously set by another user, the current program will execute the Else statements.
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/* The following function fragment locks a row, then reads it, does some unspecified processing, and then unlocks the row, before concluding. */ Equate TRUE$ To 1 Equate FALSE$ To 0 table = "SAMPLE_CUSTOMERS" key = 8 status = "" Open table To tablevar Then locked = FALSE$ Loop Lock tablevar,key Then locked = TRUE$ End Else /* set up delay for network server access */ For ctr = 1 To 1000 Next End Until Locked Repeat * we're locked, now read Read @RECORD From tablevar,key Then /* do row processing here */ End * now, unlock the row we've written back UnLock tablevar,key Else Status = Set_FSError() /* A row should always unlock first time out. */ End End Else ;* table fails to open status = Set_FSError() End ;* table taken care of Return status |
Note: Locking a table or row is not a guarantee that it will not be changed by another user. All programs must contain Lock logic to ensure that tables or rows are not simultaneously updated.
