typedef struct DBrec {
   char *dbname;    // copy of database name
   int fd;          // the database file
   SpaceMap map;    // map of free/used areas 
   NameTable names; // map names to areas + sizes
} *DB;

typedef struct Relrec {
   char *relname;   // copy of table name
   int   start;     // page index of start of table data
   int   npages;    // number of pages of table data
   ...
} *Rel;