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
312 Chapter7
Logging and Recovery
Recovery Options
Recovery Options
The logging and recovery system is used to bring databases back to the same state at the
time of a system failure; this state does not include incomplete transactions.
TurboIMAGE/XL provides several types of recovery options:
• Default recovery mode
• Dynamic roll-back recovery
• Intrinsic Level Recovery (ILR)
• Roll-forward recovery
• Roll-back recovery
• Mirror database
The recovery options are described briefly below. Dynamic roll-back recovery, ILR,
roll-forward recovery, roll-back recovery, and the mirror database are discussed in detail
later in this chapter. A brief description of these recovery and logging options is found in
appendix G, "Recovery and Logging Quick Reference." Use the information in this chapter
and in appendix G to determine which recovery and logging options to choose. The
recovery option is based on available database backup, logging resources, and performance
requirements.
Default Recovery Mode. In default recovery mode, TurboIMAGE/XL uses an MPE/iX
file system service, Transaction Management (XM), to ensure the structural integrity of
the database following a system failure. All modifications to the database (DBPUTs,
DBDELETEs, and DBUPDATEs) are automatically logged to an MPE/iX XM log file. However,
this XM log file is only written to disk when one of the following situations is true:
• A system-specified time has elapsed.
• A request is made by a process to flush the log file to disk, for example, a call to DBEND
mode 2 or 4.
• The XM buffer is full.
XM ensures that the TurboIMAGE/XL intrinsics are applied to the log file in a serial
manner. If a system failure occurs, those completed intrinsics that have not been written to
disk are not recovered. Thus, one or more completed DBPUTs, DBDELETEs, and DBUPDATEs
can be lost, but the internal structure of the database remains consistent. Recovery with
DBRECOV must be performed at system startup time before anyone modifies the database.
Dynamic Roll-Back Recovery. Dynamic roll-back recovery is a method of recovery that
uses XM. XM ensures the physical and logical integrity of the databases. Dynamic
roll-back allows a more timely recovery of databases than is possible with DBRECOV.
Dynamic roll-back eliminates the overhead incurred when a database is enabled for user
logging and permits database access to continue, even when recovering a database. It
provides the most thorough protection for logical database transactions. Dynamic
transaction can span one or more databases. The dynamic transaction spanning multiple
databases is termed dynamic multiple database transaction, or DMDBX. Dynamic
roll-back handles both program aborts and system failures without downtime for recovery,