Re: READ PREVOIUS in CLP

[CRPence <CRPbottle@xxxxxxxxx>]

On 25-May-2010 01:31, Gangasani, Bhargava wrote:
> Using CLP I can read a specific RRN/ Key record using below code.
>
> DCLF  Z5PFILEP
> OVRDBF     FILE(Z5PFILEP) TOFILE(Z5PFILEP) +
>               POSITION(*RRN 4) SHARE(*NO)
> RCVF
>
> Question is: I can place my pointer at *END of file as
>
> OVRDBF     FILE(Z5PFILEP) TOFILE(Z5PFILEP) +
>               POSITION(*END) SHARE(*NO)
>
> But How I can read the previous record. That is the Last record
> of the file.

  If the open can be shared, then write an RPG program that opens a 
program described file named THELASTROW for input only BLOCK(*NO), 
positions to *END using SETLL, reads previous twice, then returns 
without closing the file; also having coded for the special cases of 
less than three rows, to effect position at *START for one row, and 
effect read on the first row for when there are two rows.  In the CLP:

<code>

  dclf Z5PFILEP
  ovrdbf Z5PFILEP TOFILE(Z5PFILEP) share(*yes) seqonly(*no) /* +
    // POSITION() optional; allow RPG to position */
  ovrdbf TheLastRow TOFILE(Z5PFILEP) share(*yes) lvlchk(*no) /* +
    // Not an actual file, just a name for RPG to declare */
  rcvf /* CL opens shared lets RPG position w/ shared ODP */
  monmsg cpf0864 exec(goto nodata) /* handle empty file in CL */
  call RPGpgmNm  /* RPG shares open, positions, leaves open */
  rcvf /* read last record */
 dostuff: /* CL has data from last row with the last row */
   /* do whatever with data from last row, then optionally: */
  rcvf /* get CL to close A; assuming no new rows added */
  monmsg cpf0864 exec(rcvmsg pgmq(*same) msgtype(*excp) rmv(*YES))
  rclrsc /* Effect RPG close; better: use USROPN in RPG, */
         /* and code a special invocation to effect CLOSE */

Regards, Chuck