3.5 Start up and shutdown an instance
                  --------------------------------

- startup and shutdown steps: nomount, mount open. INIT.ORA file.

 - THREE STARTUP STAGES

 a) Startup Nomount

    The initSID.ora file is read.

    control files are determined at that time.

    size of the sga and pga is determined.

    Instance is started.

    SGA and background processes initialize.

 b) Startup Mount

    Opens control files defining database

    verifies that the control file is correct.

    Obtains a global "mount_db" instance lock for database.

    determines if this is the first instance mounting the
    database.

 c) Startup Open

    Opens "online" or "openable" database files defined in
    control file.

    Obtains global "startup" instance lock on the database.

    Is this the first instance opening this database?

    Verifies and opens the online redo logs.

    Instance locks are obtained for each "openable" data file.

  If first "startup" instance, perform crash recovery on all
  database files using current logs for all instances.

  Another instance can not start up during this time.
		If crash recovery is not possible because it needs older logs,
		then media recovery is needed and an error is signaled.

 - SHUTDOWNS:

     - NORMAL

         a) stops access to database

         b) WAIT UNTIL USERS EXIT

         c) purge cache and redo log, forcing dirty
            buffers to DB files

         d) dropping file locks

         e) update file headers and ongoing transactions are
            complete

         f) closes thread

         g) drops database instance lock.

     The control file and the database files are synchronized.

    - IMMEDIATE

         a) stops access to database

         b) cancel current calls and rollback

         c) purge cache and redo log, forcing dirty
            buffers to DB files

         d) dropping file locks

         e) update file headers and ongoing transactions are
            complete

         f) closes thread

         g) dropping database instance lock

    -  ABORT

         a) stops access to database

         b) dropping file locks

         c) dropping instance lock

- SQL*DBA or server manager

- Altering the database. Changing parameters when database is
  online.

- Restricted sessions.

  You may want to restrict access to the database during special
  processing period to allow high profile jobs to have the
  machines to themselves. A lot of reasons may require restricted
  access.

  In Oracle7 you may issue command:

    alter system enable restricted session;

               and

    alter system disable restricted session;

  DON'T forget to take database out of restricted mode to allow
  other normal users to work.

  If the database access was already unrestricted and you issue
  alter system disable restricted session; command then NO HARM
  done.

- Client/Server Administrator Security

  - Database connnection security (Oracle7 Server documentation
    addendum, pp.5-1 - 5-14:

    - encrypted password for connections to database servers

    - improved CONNECT INTERNAL

    - ORA_ENCRYPT_LOGIN (true/false) and DBLINK_ENCRYPT_LOGIN
      (true/false)

    - REMOTE_LOGIN_PASSWORDFILE INIT.ORA parameter.

    - CONNECT / as sysoper

    - Maintaining a password file

  - Privileged Administrative Connettions (>= release 7.1)

    orapwd FILE=<filename> PASSWORD=<password> [ENTRIES=n]

    On some platforms, the name of the password file is derived
    from the SID. In this case you CAN NOT change the password
    location.

    On other platforms the name is stored in environment
    variable, such as ORA_sid_PWFILE

    orapwd creates the initial password file <filename> and
    allows to:

         1. CONNECT SYS/<password> AS SYSDBA  (offline
               connection and normal connection to opened DBMS)

         2. Allows to add n additional users having SYSOPER or
            SYSDBA. Such user should be created in usual
            oracle manner with "CREATE USER <user>
            IDENTIFIED BY <password1>;" statement and granted
            with SYSDBA and SYSOPER privileges via GRANT SYSDBA
            TO <user> or GRANT SYSOPER TO <user> during normal
            database operationinig in opened mode. Such a
            granting creates entry for this user in <filename> as
            well as in the data dictionary.  After that this user
            can CONNECT <user>/<password1> as {SYSOPER|SYSDBA}
            internally and perform SARTUP, RECOVERY or other
            privileged operations.

     SYSOPER privilege allows to STARTUP, SHUTDOWN, ALTER
             DATABASE OPEN/MOUNT, ALTER DATABASE ARCHIVELOG,
             RECOVER and includes RESTRICTED SESSION
             privilege.
     SYSDBA privilege contains all system privileges with ADMIN
            OPTION + SYSOPER + permits CREATE DATABASE and
            time-based recovery.

     To use password file from remote location you should
     set INIT.ORA parameter:
     REMOTE_LOGIN_PASSWORDFILE={ NONE | EXCLUSIVE | SHARED }
         EXCLUSVE means that this password can be used with only
         one database
         SHARED - with multiple databases and all privileged
         users MUST connect as SYS with appropriate password.

     For encrypted connections you should set

       ORA_ENCRYPT_LOGIN environment to TRUE on client side
                    and
       DBLINK_ENCRYPT_LOGIN = TRUE (INIT.ORA on server side)