[Info-vax] Indexed RMS file question

[DJ]

On Oct 2, 9:04 am, "J Xenu" <j_x... at hotmail.com> wrote:
> It's been a LONG time since I used indexed RMS files on VMS.
>
> I have some data that I wish to place in an RMS indexed file, that is to be
> accessed randomly using keys. The way I see it, there will be 3 or 4 keys.
> Two will be text, of fixed length, with duplicates allowed. The other one or
> two are integer, more on these later.
>
> The lookups will be one of three methods:
>
> 1) Read a record that matches the first text key. Simple enough.
>
> 2) Read a record that matches both text keys. I want to read a record matching
>    both the first and second keys. There may be more than one matching record,
>    if so, I want to access them in order.
>
> 3) Using the first text key and an integer key, I want to read any record that
>    matches the first key and the integer falls within the range of the third
>    key.
>
> Best described with an example: Assume the file has the content as follows:
> (I'll leave out the second key since it's not relevant now)
>
> Key 1  Key 3  Data
>
> Alpha  1-18   data
> Alpha  19-72  more data
> Beta   1-10   bla bla
> Beta   11     more stuff
> Beta   12-32  even more data
> Beta   33-50  This is the data I want
> Beta   68-100 xxx
> Gamma  1      yyy
> Gamma  2-140  zzz
>
> Assume I do a read with Key 1 = "Beta" and Key 3 = 42. I want the read to
> return the record with data = "This is the data I want" since key 1 matches
> and Key 3 falls within the range 33-50. How do I define the keys, especially
> Key 3 without creating a duplicate record for each possible key3 value?
> The ranges are pseudo-random, not multiples of anything. There can be gaps as
> well, (for example "Beta", 62 in the example)

Dear J Xenu:

My suggestion to solve your problems is to have a primary key, first
field, be unique and be any thing you want of sequential order. Then
have you field2 be your data that contains: Alpha, Beta, or Gamma.
Your second field would contain your lower value of your range and the
next field, the third field, is your upper limit to your range, and
your fourth field is your data value. For example:

Field 1	Field 2	Field 3	Field 4	Field 5
Key0	        Key1	        Key2	        Key3	        Data Field
----------      ------------    --------        --------
----------------------------------------------
1	        Alpha	0001	        0018	        Data
2	        Alpha	0019	        0072	        More data
3	        Beta	        0001	        0010	        Bla bla
4	        Beta	        0011	        0011	        More stuff
5	        Beta	        0012	        0032	        Even more data
6	        Beta	        0033	        0050	        This is the data I
want
7	        Beta	        0068	        0100	        Xxx
8	        Gamma	0001	        0001	        Yyy
9	        Gamma	0002	        0140	        Zzz

Key 0 is primary key no duplicates.
Key 1, 2, 3 are secondary keys allow duplicates

Find Key1 = “Beta” where Key2 => 0042 and Key3 <= 0042; this should
return the value of “This is the data I want.”

Find Key1 = “Beta” where Key2 => 0033 and Key3 <= 0033; this should
return the value of “This is the data I want.”

Find Key1 = “Beta” where Key2 >= 0055 and Key3 <= 0055; this should
return the value of “Record not found”

You should create the file as sequential, fill it with data, and then
convert/sort the file to an index file with 4 keys.

I hope this helps you out. Good Luck!

Regards,
Daryl Jones