TurboIMAGE/XL Database Management System Reference Manual (30391-90012)
Table Of Contents
- 1 Introduction
- 2 Database Structure and Protection
- 3 Defining a Database
- 4 Using the Database
- 5 TurboIMAGE/XL Library Procedures
- Using TurboIMAGE/XL Intrinsics
- DBBEGIN
- DBCLOSE
- DBCONTROL
- DBDELETE
- DBEND
- DBERROR
- DBEXPLAIN
- DBFIND
- DBGET
- DBINFO
- INTRINSIC NUMBER 402
- Syntax
- Parameters
- Discussion
- Mode 101: Item Number
- Mode 102: Item Name
- Mode 103: Items in Database
- Mode 104: Items in Data Set
- Mode 113: BTREEMODE1 and Wildcard Character
- Mode 201: Set Number
- Mode 202: Set Name
- Mode 203: Sets in Database
- Mode 204: Sets with Item
- Mode 205: Set Capacity
- Mode 206: Number of Data Set Chunks
- Mode 207: Size of Data Set Chunks
- Mode 208: Primary and Actual Capacity
- Mode 209: B-Tree Attachment
- Mode 301: Paths
- Mode 302: Key or Search Item
- Mode 401: Logging
- Mode 402: ILR
- Mode 403: Dynamic Roll-Back
- Mode 404: Logging Subsystem Information
- Mode 406: Database Information
- Mode 501: Subsystem Access
- Mode 502: Critical Item Update
- Modes 8nn: Third-Party Indexing
- Mode 901: Language
- DBLOCK
- DBMEMO
- DBOPEN
- DBPUT
- DBUNLOCK
- DBUPDATE
- DBXBEGIN
- DBXEND
- DBXUNDO
- 6 Host Language Access
- Model Program
- ORDERS Database Model Program
- Main Body of Program
- Opening the Database
- Retrieving All the Records on a Chain (with Item Level Locking)
- Retrieving a Data Entry Using a Record Number
- Retrieving Master Data Using a Key Value
- Retrieving Data Serially (with Set Level Locking)
- Adding an Entry
- Updating an Entry
- Deleting an Entry
- Rewinding a Data Set
- Obtaining Database Information
- Obtaining Error Messages and Explanations
- Closing the Database
- C
- COBOL II
- Defining Data Types, Variables, and Intrinsics
- Main Body of Program
- Opening the Database
- Retrieving All the Records on a Chain (with Item Level Locking)
- Retrieving a Data Entry Using a Record Number
- Retrieving Master Data Using a Key Value
- Retrieving Data Serially (with Set Level Locking)
- Adding an Entry
- Updating an Entry
- Deleting an Entry
- Rewinding a Data Set
- Obtaining Database Information
- Obtaining Error Messages and Explanations
- Closing the Database
- FORTRAN 77
- Pascal
- RPG
- 7 Logging and Recovery
- Database Utilities Used in Logging and Recovery
- Recovery Options
- Logical Transactions
- Dynamic Roll-Back Recovery
- Intrinsic Level Recovery
- Logging Preparation
- Step 1--Checking MPE/iX Logging Configuration
- Step 2--Acquiring Logging Capability
- Step 3--Logging to Tape or Disk
- Step 4--Building a Log File for Logging to Disk
- Step 5--Creating the Log Identifier
- Step 6--Setting the Log Identifier
- Step 7--Setting Flags for the Database Backup Copy
- Step 8--Making a Database Backup Copy
- TurboSTORE/iX 7x24 True-Online Backup
- Logging Status
- Logging Maintenance
- Roll-Forward Recovery
- Roll-Back Recovery
- DBRECOV Commands Used with Roll-Forward and Roll-Back Recovery
- Recovery Tables
- Post-Recovery Options
- The Mirror Database
- 8 Using the Database Utilities
- Restructuring the Database with TurboIMAGE/XL Utilities
- Summary of Utility Routines
- Utility Program Operation
- DBLOAD
- DBRECOV
- >CONTROL
- >EXIT
- >FILE
- >RECOVER
- >ROLLBACK
- >RUN
- DBRESTOR
- DBSTORE
- DBUNLOAD
- DBUTIL
- >>ACTIVATE
- >>ADDINDEX
- >>CREATE
- >>DEACTIVATE
- >>DETACH
- >>DISABLE
- >>DROPINDEX
- >>ENABLE
- >>ERASE
- >>EXIT
- >>HELP
- >>MOVE
- >>PURGE
- >>REBUILDINDEX
- >>REDO
- >>RELEASE
- >>SECURE
- >>SET
- >>SHOW
- Syntax
- Parameters
- Example (Show Users)
- Example Discussion
- Example (Show All)
- Example Discussion
- Example (Show Capacity)
- Format of Show Device List
- Example (Show Device)
- Format of Show Indices
- Example (Show Indices)
- Format of Show Locks List
- Example 1 (Show Locks)
- Example 1 Discussion
- Example 2 (Show Locks)
- Example 2 Discussion
- >>VERIFY
- 9 Using a Remote Database
- 10 Internal Structures and Techniques
- 11 B-Tree Indices
- A Error Messages
- B Results of Multiple Access
- C Database Design Considerations
- D Multiple Calls to DBLOCK
- E TurboIMAGE/XL Log Record Formats
- F MPE/iX Log Record Formats
- G Recovery and Logging Quick Reference
- H TurboIMAGE/XL versus TurboIMAGE/V
Chapter 4 99
Using the Database
Opening the Database
• Access Mode 7. The database is opened for exclusive read access. No other users can
access the database concurrently. Access mode 7 operates the same as access mode 3,
except that the DBUPDATE, DBPUT, and DBDELETE procedures, which alter the
database, are disabled for the access mode 7 user.
• Access Mode 8. The database is opened for shared read access. Concurrent users must
either be in access mode 6 or 8, or using the TurboIMAGE/XL utility, DBSTORE.
TurboIMAGE/XL procedures that alter the database are not permitted. Because access
mode 8 allows only concurrent readers, a user program with this access mode can be
assured that the database values it reads are unchanging.
Selecting a Database Access Mode
When deciding which access mode to use, the following are two important considerations:
• Use the minimum capability required to accomplish the task. For example, select a
read-only access mode (5, 6, 7, or 8) if the program does not alter the database in any
way. Read access modes allow concurrent database STORE operations and do not set the
MPE/iX "file modified" flag.
• Allow concurrent users to have as much capability as is required for successful
completion of the task. If the task is merely browsing through the database, producing a
quick report, or accessing an unchanging portion of the database, choose an access mode
that allows concurrent users to make database modifications to other parts of the
database. Allowing concurrent read-only access (modes 2, 4, and 8) can be appropriate
in many situations. For programs that must be assured of no concurrent structural
changes, but can tolerate simultaneous updates to entries, mode 2 is suitable. Locking
can be used to control simultaneous updates to a data entry. If it is necessary to make
additions or deletions to a database from concurrent multiple processes, modes 1 and 5
must be used. Fully exclusive operation (modes 3 and 7) are available if needed.
The following access mode selection guidelines are organized according to the task to be
performed. For some tasks, one of several modes can be selected depending on the
concurrent activity allowed with each mode.
• Programs that perform operations, which include adding and deleting entries or which
need to update detail data set search and sort items via the critical item update
(CIUPDATE) option, should open with mode 1, 3, or 4. Consider the following when
choosing among access modes 1, 3, and 4:
Access Mode 1 Can be used if other processes need to add and delete entries
simultaneously. In this case, the affected parts of the database must be
locked while performing updates, additions, or deletions.
Access Mode 3 Can be used if the program must have exclusive access to the database.
Access Mode 4 Can be used if exclusive ability to change the database is required but
access mode 6 processes need to be able to read the database while
changes are being made.
• Programs that locate, read, and replace data in existing entries but do not need to add
or delete any entries, and do not want any other processes to do so, should open the
database in access mode 2. Consider the following when choosing access mode 2: