Dear All
Hope every SAP basis consultants / users do well . may i'm still beginner in SAP Basis world , but i think it is very good to share our knowledge between us 
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Note : if you get bored of reading long articles , kindly forgive me .
one of my big issue i daily faced in our SAP system . ( Spool is full )
in our SAP system we have service user for third party application for Mobility sales using Handheld terminals , this user allow the third party to do some tasks in SAP ( create Sales orders , print Sales order , create Invoice , cash Journal tasks , ..... ) usually printing done through special printers connected to Handheld , but also Sales orders printed virtually in our SAP system with Output Stat " - " which mean " - Not yet sent to the host system (no output request exists ".
from my deep careful reading to solve this issue , i got three solutions . one is temporary solution , the second not bad solution , the last one is wonderful solution
First solution :
delete old spool requests manually
Tcode SP01 - and enter old period the execute
the select all spool requests no. , then delete
as you see , it is not perfect solution .
Second solution :
maximize the spool range number .
use Tcode SNRO , object: SPO_NUM then use NUMBER RANGE option .
press INTERVALS change option 
you can increase the range of intervals
as you see it is not the best solution , because you may forget the maximum range number & in future you may surprise that the spool is full .
Third Solution :
briefly it depend on delete old spool requests automatically , i created periodic job for executing SAP standard program with my own Variant .
use Tcode SA38 , for execute RSPO1041 program
you can customize control the program ( user , server , client , spool request state , days , .... ) then save your Variant
you can create Background Job with your estimated execution time , to execute RSPO1041 program with your own saved Variant .
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RZ20 may useful for you to check the used spool requests parentage
kindly forgive me for bad English typing or meaning .
Finally, hope this was helpful .
appreciate for all your time