Any idea whether this parameter can be set / adjusted and where please?

Which problem do you have?
Error messages?

Many thanks the errors are pasted below.

STORAGE_PARAMETERS_WRONG_SET

The current program had to be terminated because of an
error when installing the R/3 System.
The program had already requested 78016400 bytes from the operating
system with 'malloc' when the operating system reported after a
further memory request that there was no more memory space
available.
Active calls in SAP kernel


=> 64 bit R/3 Kernel
=> 64 bit AIX Kernel
=> Heap limit = 134217728
=> Stack limit = 33554432
=> Core limit = unlimited
=> File size limit = unlimited
=> Heap address = 0x117ff81e0
=> Stack address = 0xfffffffffff5870
=> Stack low = 0xfffffffffff5870
=> Stack high = 0xffffffffffff760
=> Stack Trace:

Also

EXSORT_NOT_ENOUGH_MEMORY (!! the number of rows this abap querry retrieved : SY-DBCNT 1125533 )

Error in the SAP Basis system
ABAP/4 processor detected an internal system error.
The current ABAP program "AQ10ZFINVENTORY=GRIRREPORT==== " had to be terminated
because the ABAP
processor discovered an invalid system state.

The current ABAP/4 program was meant to sort a dataset (internal table
or extract). For reasons of capacity, this was not possible due to
insufficient main storage space. Therefore, the
external sort was called and resulted in the following error:
the following error:

SAP runtime system internal error.

Sorry for the late reply, I'm very busy.

There are three general reasons for runtime error STORAGE_PARAMETERS_WRONG_SET:

1) Insufficient memory size
2) Improper memory settings
3) Very huge amount of processed data

Please check the following SAP notes:

146289 Parameter Recommendations for 64-Bit SAP Kernel
425207 SAP memory management, current parameter ranges
789477 Large extended memory on AIX (64-bit) as of kernel 6.20
146528 Configuration of R/3 on hosts with much RAM
153641 Swap space requirement for R/3 64-bit kernel

193529 Sort as of 4.5A / EXSORT_NOT_ENOUGH_MEMORY
51959 STORAGE_PARAMETERS_WRONG_SET
44528 STORAGE_PARAMETERS_WRONG_SET

You may also run the following utility and paste the output in here:
sappfpar check pf=<full path to instance profile>