Re: READ(E) and locked records

[Scott Klement <klemscot@xxxxxxxxxxxx>]

On Fri, 5 Oct 2001, Robin Coles wrote:
>
> With READ and an indicator, if the record happened to be locked the user
> got an error message that was ugly but allowed a retry.  It happened so
> infrequently and recovery was so painless that we just accepted it.
> We've recently switched to using READ(E) and %EoF etc, using code
> similar to:
>
> Read(E)       File
> Dow           Not %EoF
> ... Some stuff here
> Update        File
> Read(E)       File
> EndDo
>
> but now we don't get the error message if there's a lock, and we fall
> through the DoW loop ending up with an update without prior read or
> chain.


The reason that you're not getting a "lock error message" is because
you're specifying "(E)", which means to trap all errors.   This is the
same (and has the same results) as placing a 2nd indicator in the 'Lo'
indicator position.

i.e., these two code snippets are functionally the same:

     C                   read      file                                 0102
     C                   dow       *in02 = *On
     C                   read      file                                 0102
     c                   enddo

     c                   read(e)   file
     c                   dow       not %eof(file)
     c                   read(e)   file
     c                   enddo

This is a bad idea, as you've noted, because in both cases you're telling
it that _you_ want to handle any errors (either by specifying (E) or by
specifying indicator 01)  -- but then you're not handling those errors.

Instead, if you're not going to handle them, let the operating system take
it's default action.    These two snippets of code do that:

     c                   read      file                                   02
     C                   dow       *in02 = *On
     c                   read      file                                   02
     c                   enddo

     c                   read      file
     c                   dow       not %eof(file)
     c                   read      file
     c                   enddo

Does that make sense?  (Or did I miss the point completely?)