Technical data

Managing Storage Media
9.14 Using Interrupt Priority Level C (IPC)
9.14.3 Entering the Debugger
To use the XDELTA debugger, enter the following commands from the console
terminal:
IPC> X
You are now in the debugger. The X command transfers control to the debugging
tool XDELTA (provided it was loaded with the system by setting the appropriate
value in the boot file). If XDELTA has not been loaded, the prompt IPC> is
reissued. For example:
IPC> X
IPC>
To exit from the debugger, press Ctrl/Z:
Ctrl/Z
)
For information about the XDelta debugger, refer to the OpenVMS Delta/XDelta
Debugger Manual.
9.15 Using the Bad Block Locator Utility to Detect Media Errors
The DCL command ANALYZE/MEDIA invokes the optional Bad Block Locator
utility (BAD), which analyzes block-addressable media and records the location of
blocks that cannot reliably store data.
Note
Many newer devices automatically check for bad blocks; therefore, BAD is
more useful with older devices that do not check for bad blocks.
To test the blocks on a volume, ANALYZE/MEDIA performs the following tasks:
• Writes a test pattern to each block on the media
• Reads the contents of the block into a buffer
• Compares the data read back with the data written
If the data does not compare exactly, a block cannot reliably store data.
When the Bad Block Locator utility locates a bad block, it records the address of
the block. Consecutive bad blocks are recorded as single entries for non-last-track
devices. After it finishes testing the disk, BAD writes the addresses of the bad
blocks into a file called the detected bad block file (DBBF).
Caution
Testing a volume for bad blocks destroys its contents. However, you can
update the detected bad block file (DBBF) without erasing the contents of
the volume by using the ANALYZE/MEDIA qualifiers /NOEXERCISE and
/BAD_BLOCKS.
9–80 Managing Storage Media