. Focus attention on the relatively few items that can satisfy the majority of onboard demands for material .   Provide   for   the   accumulation   of   accurate consumption  data  required  for  supply,  edit,  audit,  and SIM  (SEAS)  system  and  the  3-M  program  and  to maintain  adequate  supply  levels l   Establish   a   historical   demand   file   for accumulating  usage  data  for  not  carried  material . Make sure there is COSAL support for the parent equipment of each needed repair part .  Reduce  physical  inventory  requirements  and prescribe  standard  physical  inventory  requirements . Provide for effective management of controlled equipage,   presentation   silver,   and   depot   level repairable .  Reduce  the  number  of  stock  record  management data  changes . Prescribe the NAVSUP Form 1250-1 as the issue request  document  and  as  the  normal  requisitioning document of the nonautomated ships .  Automated  ships  except  those  in  the  submarine force SHIPBOARD  STOCK  LEVELS The  basic  Navy  policy  governing  the  range  and depth of stock material that your ship is required to carry for self-support is stated in OPNAVINST 4441.12. In essence,  the  range  and  depth  of  nondemand-based  items must  be  limited  to  COSAL  authorized  items  and quantities.  Demand-based  items  can  be  determined from usage and prescribed average endurance levels. Levels  of  supply  can  be  expressed  in  either  of  two ways. .  Numerically–so  many  units  of  an  item .  Endurance–period  of  time  for  which  supply support  is  required Both of these terms are used. However, endurance is a general  term  and  must  be  converted  to  numerical quantities before meaningful levels of supply can be determined. Figure 8-1 illustrates the various terms used in computing  stock  levels.  The  operating  level  is  the  first factor since it represents the quantity that is required to sustain  operations  for  a  required  period  of  time. Endurance  requirements  are  issued  by  the  Chief  of Naval Operations and are shown in figure 8-2. The safety level is an additional quantity added to the  operating  level  to  make  sure  of  continued  support even though normal replenishment is delayed or the ship experiences a greater than normal demand. These two levels, combined, constitute the stockage objective, or the maximum quantity of stock that should be on hand. The third factor that must be considered is the order and   shipping   time   for   replenishment   stock.   The anticipated quantity of stores that will be consumed during   the   time   required   for   the   replenishment requisition   to   reach   the   supply   activity   and   the replenishment stock to reach your ship is added to the stockage  objective  quantity.  The  resulting  requisitioning objective is the maximum quantity of stock to be on hand and on order at any given time. Quantity  of  material  required  to sustain operations in the interval OPERATING between  requisitions  or  the  arrival LEVEL OF of  successive  shipments. SUPPLY Quantity  required  to  permit  con- tinued  operations  during  interrup- tions of replenishment or unpredictable   demands. Quantity of material consumed during normal order and shipping time. SAFETY LEVEL OF SUPPLY STOCKAGE OBJECTIVE   REQUISITIONING   OBJECTIVE Figure 8-1.—Levels of supply. 8-2