RPGIV编程问题百解(22)一个程序中，对同一个文件并行操作

RPGIV编程问题百解(22)一个程序中，对同一个文件并行操作

 

问题：

 

一个问题一直困绕着我，在一个程序中，对同一个文件可以操作码？

 

回答1：

 

FTestPF    if   e           k disk                                     
FTestPFAlt if   e           k disk     Usropn                          
F                                      Rename(TSTRCD : TSTRCDALT )     
D OvrDbf        C                   CONST('Ovrdbf File(TESTPFALT) Tofile-
D                                    (*LIBL/TESTPF) OPNSCOPE(*JOB)')  

Downside is that TestPFAlt would have to be overriden (both to compile and
run), but it allows you to read the same file throug two open data paths:

  Read testpf;
  Read testPFAlt; // actually a second ODP to TestPF

 

回答2：

 

If you are at 6.1 (probably not, eh?), then you can use EXTDESC and EXTFILE.

FTestPF    if   e             disk          
FTestPF2   if   e             disk  extdesc('TESTPF')
F                                   extfile(*extdesc)
F                                   rename(TSTRCD:TSTRCD2)

EXTDESC is new with 6.1 and it tells the compiler where to get the external
field definitions.

 

回答3：

 

Try using ExtFile, Rename and Prefix keywords for the second instance of your
file and use external DS for one or both of them.

FTestPF    if   e             disk          
FTestPF2   if   e             disk 
F                                   extfile('TESTPF')
F                                   rename(TSTRCD:TSTRCD2)
F                                   Prefix(PF2)

D DsPF2         E DS                  ExtName(TestPF)  
D                                     Prefix(PF2)

 

回答4：

 

FTestPF    if   e             disk  PREFIX('PF.')        
FTestPF2   if   e             disk  PREFIX('PF2.')
F                                   extfile('TESTPF')
F                                   rename(TSTRCD:TSTRCD2)
D PF        DS         LikeRec(TSTRCD)
D PF2       DS         LikeRec(TSTRCD)  // Could also use LikeREC(TSTRCD2)

This assumes you have a logical TESTPF2 over the physical TESTPF which is
nothing more than a format file in this case.