SQLite

  /*
  ** Allocate space for memory structures
  */
  szScratch =
       nMaxCells*sizeof(u8*)                       /* apCell */
     + nMaxCells*sizeof(u16)                       /* szCell */
     + pBt->pageSize;                              /* aSpace1 */
  assert( szScratch<=16896 || szScratch<=6*pBt->pageSize );
  apCell = sqlite3ScratchMalloc( szScratch ); 
  if( apCell==0 ){
    rc = SQLITE_NOMEM;
    goto balance_cleanup;
  }
  szCell = (u16*)&apCell[nMaxCells];
  aSpace1 = (u8*)&szCell[nMaxCells];

** scratch memory.  There are three arguments:  A pointer an 8-byte
** aligned memory buffer from which the scratch allocations will be
** drawn, the size of each scratch allocation (sz),
** and the maximum number of scratch allocations (N).  The sz
** argument must be a multiple of 16.
** The first argument must be a pointer to an 8-byte aligned buffer
** of at least sz*N bytes of memory.
** ^SQLite will use no more than two scratch buffers per thread.  So
** N should be set to twice the expected maximum number of threads.
** ^SQLite will never require a scratch buffer that is more than 6
** times the database page size. ^If SQLite needs needs additional
** ^SQLite will not use more than two scratch buffers per thread and not
** more than one scratch buffer per thread when not performing
** a [checkpoint] in [WAL mode].
** ^SQLite will never request a scratch buffer that is more than 6
** times the database page size, except when performing a [checkpoint]
** in [WAL mode] when the scratch buffer request size is a small fraction
** of the size of the WAL file.
** ^If SQLite needs needs additional
** scratch memory beyond what is provided by this configuration option, then 
** [sqlite3_malloc()] will be used to obtain the memory needed.</dd>
**
** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
** <dd> ^This option specifies a static memory buffer that SQLite can use for
** the database page cache with the default page cache implementation.  
** This configuration should not be used if an application-define page