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nvlogpg(8)
NAME
nvlogpg - Displays the log file of an AdvFS domain
SYNOPSIS
/sbin/advfs/nvlogpg log_id
/sbin/advfs/nvlogpg [-v | -B] log_id page [record_offset [-f]]
/sbin/advfs/nvlogpg [-v | -B] log_id { -R | -a }
/sbin/advfs/nvlogpg [-v | -B] log_id { -s | -e } [page_offset]
/sbin/advfs/nvlogpg domain_id | volume_id -d dump_file
/sbin/advfs/nvlogpg [-v | -B] volume_id -b block
OPTIONS
-a Displays all the pages in the log file.
-B Brief. Displays only the transaction ID for each log file entry.
-b block
Specifies the logical block number of a disk block on an AdvFS volume.
-d dump_file
Specifies the name of a file that will hold the contents of the
specified log file.
-e Displays the last active record in the log file--the end of the log
file.
-f Displays all subtransactions following the parent transaction.
-R Displays the active records.
-s Displays the first active record in the log file--the start of the log
file.
-v Verbose. Displays all the data in a specified log, page, or record.
OPERANDS
log_id
Specifies a log file in an AdvFS domain or a log file that has been
saved by the utility as a dump_file. Use the following format:
domain_id | volume_id | [-F] dump_file
Specify the -F option to force the utility to interpret the name
you supply as a file name.
domain_id
Specifies an AdvFS file domain using the following format:
[-r] [-D] domain
By default, the utility opens all volumes using block device
special files. Specify the -r option to operate on the raw device
(character device special file) of the domain instead of the block
device. Specify the [-D] option to force the utility to interpret
the name you supply in the domain argument as a domain name.
volume_id
Specifies an AdvFS volume using the following format:
[-V] volume | domain_id volume_index
Specify the -V option to force the utility to interpret the name
you supply in the volume argument as a volume name. The volume name
argument also can be a full or partial path for the volume, for
example /dev/disk/dsk12a or dsk12a. Specifying a partial path name
always opens the character device special file.
Alternatively, specify the volume by using arguments for its
domain, domain_id, and its volume index number, volume_index.
dump_file
Specifies the name of a file that contains the output from this
utility.
page
Specifies the file page number of a file.
page_offset
Specifies the offset relative to the start or the end of the active
region in the log file.
record_offset
Specifies a byte offset in a page of the log file.
DESCRIPTION
The nvlogpg command locates the log file of an AdvFS file domain and
displays records from it in various ways.
The log file for a domain is a bitfile, organized as an array of 8 Kb disk
pages. Each page consists of a fixed-size header record, a number of
variable-sized data records, and a fixed-size trailer record. Each data
record consists of a fixed-size header and a variable amount of data.
The log file for a domain contains the metadata, the log, of each
transaction. Before a transaction is written to disk, its logged metadata
is written to disk. Because the log of a transaction contains the
information necessary to redo the transaction, the file system can maintain
consistency on disk and recover from system failures when they occur. These
transactions and the metadata they include are used to replay transactions
that did not complete, for example if the system crashed, when the domain
is next activated.
Displaying a Summary
You can specify a domain or volume name to display a summary of the log
file that includes its location, size, and the location of its starting and
ending records.
For example, to display a summary of the log file for domain domain_1,
enter the following command:
# /sbin/advfs/nvlogpg domain_1
Displaying Log File Pages and Records
There are several ways you can specify log file pages and records.
To display page five of a log file for a domain that you know is on device
rz5a, enter the following command:
# /sbin/advfs/nvlogpg rz5a 5
To display the record at byte offset 234 in page seven of the log file in
the domain named domain_1, enter the following command:
# /sbin/advfs/nvlogpg domain_1 7 234
You can use the command to find the start or the end of the active log.
The start of the log is the first record whose data is not yet written to
the metadata files. The end of the log is the last record that has been
written to the log. For example, to display the first record in domain
domain_1 whose record is not yet written to metadata files, enter the
following command:
# /sbin/advfs/nvlogpg domain_1 -s
To display the end of the log in domain domain_1--the last record that has
been written to the log--enter the following command:
# /sbin/advfs/nvlogpg domain_1 -e
You can use the utility to display pages and records that are after or
before after the start or the end of the active log. For example, to
display the second page after the start of the log file for domain_1, enter
the following command:
# /sbin/advfs/nvlogpg domain_1 -s 2
To display the page before the end of the log for domain_1, enter the
following comand:
# /sbin/advfs/nvlogpg domain_1 -e -1
To display the record at byte offset 234 on the page of the log that holds
the last log record in the log file for domain_1, enter the following
command:
# /sbin/advfs/nvlogpg domain_1 -e 0 234
The page offset is relative to the page that contains the start and end
records of the log file. The record offset is relative to the specified
page.
Following a Transaction
The utility can follow the log records that belong to one transaction. For
example, you can follow a set of log records from one transaction by
specifying a record and the -f option.
Specify one particular log record and use the -f option. For example, to
display the log record at page 1, byte offset 128, and all the following
records that belong to the same transaction, enter:
# /sbin/advfs/nvlogpg domain_1 1 128 -f
Because the -s option also specifies one record, the -f option can be used
with it. For example:
# /sbin/advfs/nvlogpg domain_1 -s -f
Saving and Examining the Log File
You can use the nvlogpg command to write the log file to another file, a
dump_file, and later use the command to examine it.
For example, you can extract the log file for domain domain_1 and write it
to a file named domain_1_log by entering the following command:
# /sbin/advfs/nvlogpg domain_1 -d domain_1_log
Later, you can examine the log file you extracted. Use the same command
syntax on the file as you did for the log in the domain, except you use the
-F option to force the utility to interpret the name as a file name, in
case there is a domain or volume with the same name.
For example, you can display a summary of the file, domain_1_log by
entering the following command:
# /sbin/advfs/nvlogpg -F domain_1_log
NOTES
An active domain, which is a domain with one or more of its filesets
mounted, has all of its volumes opened using block device special files.
These devices cannot be opened a second time without first being unmounted.
However, the character device special files for the volumes can be opened
more than once while still mounted.
It can be misleading to use this utility on a domain with mounted filesets
because the utility does not synchronize its read requests with AdvFS file
domain read and write requests.
For example, the AdvFS can be writing to the disk as the utility is reading
from the disk. Therefore, when you run the utility, metadata may not have
been flushed in time for the utility to read it and consecutive reads of
the same file page may return unpredictable or contradictory results. (The
domain is not harmed.)
To avoid this problem, unmount all the fileset in the domain before using
this utility.
RESTRICTIONS
The utility can fail to open a block device, even when there are no
filesets mounted for the domain and the AdvFS daemon, advfsd, is running.
The daemon, as it runs, activates the domain for a brief time. If the
nvlogpg utility fails in this situation, run it again.
EXIT STATUS
The utility returns a 0 (zero) on success, otherwise it returns a nonzero
value and an error diagnostic.
FILES
/sbin/advfs/nvlogpg
Specifies the command path.
/etc/fdmns/domain_name
Specifies the volumes in the domain.
SEE ALSO
Commands: nvbmtpg(8), nvfragpg(8), tag2name(8), vfilepg(8), vsbmpg(8)
Files: advfs(4)
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