IBM 000-8697 Manual Do Utilizador

Data Consistency, Recovery, and Migration

When you request a logical log backup, you are prompted to mount a tape on
the tape device specified as

LTAPEDEV

 in the configuration file. The tbtape

process prompts you to verify that the tape device is ready.

If the tape is new, the tbtape utility process writes a tape header page to the
device. This tape header page contains the following information:

■

The tape device block size (

LTAPEBLK

)

■

The size of tape (

LTAPESIZE

)

■

A flag that indicates the tape is for logical log backup

■

A timestamp that indicates the date

The tbtape process locates the oldest logical log file that has been used but
not backed up (status

U

).

OnLine backs up all full logical logs. If more than one tape is needed, OnLine
provides you with labelling information for the full tape and prompts you to
mount a new tape.

If Continuous-Logging is chosen, tbtape begins to back up all currently full
log files. The tbtape process then waits for the current log to become full. As
each log file becomes full, tbtape automatically initiates a back up.

The tbtape process begins by comparing the identification number of the log
file it is backing up with every entry on every blobspace free-map page. The
tbtape

 process is looking for blobpages that were allocated during the time

this logical log file was the current log file. (Refer to

for more infor-

mation about the blobspace free-map page and its role in logical log file
backups.)