Weigh the benefits of whether something in this category must use large pages as a result of  the system-level costs of tying up real storage. A balance exists between the performance of  a process that uses large pages and the performance of the remaining work on the system. On z14 ZR1 servers, 1 MB large pages become pageable if Virtual Flash Memory$^{5}$ is  available and enabled. They are available only for 64-bit virtual private storage, such as virtual  memory that is greater than 2 GB.  It is easy to assume that increasing the TLB size is a feasible option to deal with TLB-miss  situations. However, this process is not as straightforward as it seems. As the size of the TLB  increases, so does the processor usage that is involved in managing the TLB’s contents.  Correct sizing of the TLB is subject to complex statistical modeling to find the optimal tradeoff  between size and performance. Main storage is addressable by programs and storage that is not directly addressable by  programs. Non-addressable storage includes the hardware system area (HSA).  Main storage provides the following functions: Main storage can be accessed by all processors, but cannot be shared between LPARs. Any  system image (LPAR) must include a defined main storage size. This defined main storage is  allocated exclusively to the LPAR during partition activation. The HSA is a reserved storage area that contains system LIC and configuration-dependent  control blocks. On z14 ZR1 servers, the HSA has a fixed size of 64 GB and is not part of the  client purchased memory. The fixed size of the HSA eliminates planning for future expansion of the HSA because the  hardware configuration definition (HCD) and input/output configuration program (IOCP)  always reserves space for the following items: 3.6.2 Main storage 3.6.3 Hardware system area GLYPH<SM590000> Data storage and retrieval for PUs and I/O GLYPH<SM590000> Communication with PUs and I/O GLYPH<SM590000> Communication with and control of optional expanded storage GLYPH<SM590000> Error checking and correction GLYPH<SM590000> Three channel subsystems (CSSs) GLYPH<SM590000> A total of 15 LPARs in the first two CSSs and 10 LPARs for the third CSS for a total of 40  LPARs per system GLYPH<SM590000> Subchannel set 0 with 63.75-K devices in each CSS GLYPH<SM590000> Subchannel set 1 with 64-K devices in each CSS GLYPH<SM590000> Subchannel set 2 with 64-K devices in each CSS The HSA includes sufficient reserved space to allow for dynamic I/O reconfiguration changes  to the maximum capability of the processor. 5 Virtual Flash Memory replaced IBM zFlash Express for z14. No carry forward of zFlash Express exists. 96  IBM 14 Model ZR1 Technical Guide