Recovering a Data Base

TurboIMAGE/XL is designed to main tain the integrity of its data bases. Ho wever, it is possible that data or structural information can be lost during a hardw are failure or an operating system crash. It is highly recommended that y ou regularly bac kup a database.

You can maintain the database b y copying it to magnetic tape using DBSTORE at regular intervals. If necessary, you can restore the database using DBRESTOR . This restores the database to its state at the time it w as last stored. You can use this method more often than system backups are done to main tain recent copies of the database and minimize the n umber of transactions that ma y be lost.

To recover changes made after the last bac kup, you must do one of the follo wing: Rerun all jobs that modi￿ed the database since the last time it w as stored.

If transaction logging w as enabled, run the DBRECO V utility.

You can execute the transaction logging and reco very system to return a database to a state near that at the time of system failure. The logging system pro vides a mechanism to log database transactions to a log￿le on magnetic tape or disc. If y ou must restore the database, ￿rst restore the bac kup data base copy and then run the reco very program, DBRECO V. This re-enters transactions from the log ￿le against the data base. It also allo ws you to create individual user reco very ￿les, providing information to users that enables them to ￿gure out where to resume transactions.

The database administrator is responsible for enabling and disabling the logging and reco very processes and generating bac kup database copies. This mak es logging a global function controlled at the database lev el, rather than at the individual user lev el.

QUERY/V

QUERY/V is a database managemen t subsystem used for retriev al and reporting of data. Y ou can use it to retriev e, report on, update, add, and delete data in a database and displa y the database structure. It pro vides you with the abilit y to:

Inquire into a database without writing special programs

Make low-volume data modi￿cation and load new data

Generate reports comparable to those that man y languages produce

Debug new application programs

The report generation capabilit y of QUERY/V allows you to select data on a basis of compound logical comparison. Once selected, y ou can control which items are reported and how they are formatted on the report.

You can run QUERY/V by entering:

:RUN QUERY.PUB.SYS

Frequently used QUERY/V commands are:

HELP, which explains QUERY/V commands

DEFINE , which prompts for needed en vironment information

7-18 Data Management