HP 3000 Manuals

IMAGE/SQL Administration Guide

How IMAGE/SQL Works 

IMAGE/SQL users can select data in mapped tables in the same way that
data in ALLBASE/SQL tables is selected.

To understand how this is accomplished, you need to know:

   *   What files are used by IMAGE/SQL
   *   How IMAGE/SQL files are used
   *   What takes place during the attach/detach process
   *   How IMAGE/SQL maps TurboIMAGE/XL security
   *   How IMAGE/SQL maps TurboIMAGE/XL data types
   *   What takes place at run time

IMAGE/SQL Files 

IMAGE/SQL creates two files:  the ATCINFO file with a default name of
DBEnvironmentNameCR in the same group and account as the DBEnvironment
and DBNameTC in the same group and account as the TurboIMAGE/XL database.
This is shown in Figure 3-1 .


          Figure 3-1.  Files Created by IMAGE/SQL 

These files contain information about the relationships between all
attached TurboIMAGE/XL databases and their DBEnvironments.  Specifically:

ATCINFO       is a permanent privileged file in the same group and
              account as the DBEnvironment.  It contains mapping
              information about each TurboIMAGE/XL database attached to
              the DBEnvironment.  One ATCINFO file exists for each
              DBEnvironment.

              [REV BEG]

              It is named DBEnvironmentNameCR where DBEnvironmentName is
              up to six characters of the actual DBEnvironmentName unless
              a file equation has been set before the attach.  The
              ATCINFO filename is placed in the DBECon file of the
              DBEnvironment so that it can be located whenever IMAGE/SQL
              needs to use or update the information in this file.[REV
              END]

DBNameTC      is a permanent privileged file in the same group and
              account as the TurboIMAGE/XL database.  It contains the
              fully qualified names of the DBEnvironments to which the
              TurboIMAGE/XL database is attached.  This information is
              used to let external utilities such as DBUTIL know that the
              database is attached to one or more DBEnvironments.

What Takes Place During an Attach? 

An attach is the process that establishes the connection between the
TurboIMAGE/XL database and the DBEnvironment.  Figure 3-2  shows a
TurboIMAGE/XL database and DBEnvironment before the TurboIMAGE/XL
database is attached.


          Figure 3-2.  A TurboIMAGE/XL Database and a DBEnvironment Before the Attach 

When the TurboIMAGE/XL database is attached to the DBEnvironment, several
events take place:

   1.  The ATCINFO (DBEnvironmentNameCR) and DBNameTC files are created.

   2.  Definitions of the TurboIMAGE/XL mapped tables are placed in the
       system catalog of the DBEnvironment.  These entries in the system
       catalog identify the tables as mapped tables.  The naming
       convention for SQL tables is OwnerName.TableName.  By
       default, in mapped tables, IMAGE/SQL specifies the database
       name as the owner name and the data set name as the table
       name.  Thus, the naming convention for mapped tables is
       MappedDatabaseName.MappedDataSetName.  (At attach time, you must
       substitute a different owner name if an already attached database
       has the same name.)[REV BEG]

   3.  Definitions of the TurboIMAGE/XL mapped columns are placed in the
       system catalog of the DBEnvironment.

   4.  Definitions for hash indices on TurboIMAGE/XL master key item and
       detail search items are entered into the system catalog for the
       DBEnvironment.  All master keys, except P and Z data types, are
       entered as unique hash indices.  Definitions for detail search
       items, as well as master P and Z key types, are entered as
       non-unique hash indices.  These definitions are in the views
       SYSTEM.IMAGEKEY and CATALOG.IMAGEKEY. With the hash indices, the
       performance at run-time is much better when the equality operator
       is used with the SQL statements.

       If the B-Tree index is created for the key item of a master data
       set using TurboIMAGE/XL, a definition for a unique B-Tree index is
       placed in the system catalog.  In addition, definitions for
       non-unique B-Tree indices for all of the search items of the
       detail data sets to which this key item has a path are added in
       the system catalog.  The definitions for these B-Tree indices are
       in the views SYSTEM.INDEX and CATALOG.INDEX of the system catalog.

   5.  If the database is enabled for third-party indexing, definitions
       for these indices are also added to the system catalog of the
       DBEnvironment, except for keyword indices and those indices for
       which the third-party provides no information.  These definitions
       may be for unique or non-unique indices.  The definitions are in
       the views SYSTEM.TPINDEX and CATALOG.TPINDEX of the system
       catalog.  The definitions for third-party indices are also placed
       in the system catalogs of other DBEnvironments to which the
       database is attached.
       [REV END]

   6.  The TurboIMAGE/XL database creator (DBC) is defined in the ATCINFO
       file as an IMAGE/SQL user.  For security reasons, all other
       IMAGE/SQL users must be explicitly added by the DBC.

Figure 3-3 shows an attached database.


          Figure 3-3.  An Attached TurboIMAGE/XL Database 

What Takes Place During a Detach? 

When a database is detached, you can no longer use SQL to access
TurboIMAGE/XL data.  All views based on mapped tables are dropped.  This
includes views created by users, as well as IMAGE/SQL-created views.
Mapped table definitions are removed from the system catalog and all
mapping information about the detached TurboIMAGE/XL database is removed
from the ATCINFO file.[REV BEG] This results in the removal of
definitions of hash, B-Tree, and third-party indices from the system
catalog.

If you detach the only TurboIMAGE/XL database attached to the
DBEnvironment, the ATCINFO file is deleted, and its name is removed from
the DBECon file.  If you detach the TurboIMAGE/XL database from the only
DBEnvironment it is attached to, the DBNameTC file is deleted.

If you plan to restructure the database, or if you want to remove all
mapping information about the database from the ATCINFO file, detach the
database.  If you only want to change the capacity of a data set, you do
not need to detach the database.
[REV END]

When the database is detached, all customized mapping information
(alternative data types and added IMAGE/SQL users) is lost and must be
remapped when the database is reattached.  IMAGE/SQL utility command
files are useful for this purpose (refer to Tasks 13 and 14 in Chapter
2).

To protect database security, be sure command files that contain
passwords and other sensitive information are carefully controlled.  (A
message notifies you when IMAGE/SQL commands containing maintenance words
or passwords have been logged.)

MPE/iX 5.5 Documentation