nvlogpg(8)						      System Manager's Manual							nvlogpg(8)

NAME

       nvlogpg - Display the log file of an AdvFS file 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

       Specifies  that all the pages in the log file be displayed.  Brief.  Specifies that only the transaction id for each log file entry be dis-
       played.	Specifies the logical block number of a disk block on an AdvFS volume.	Specifies the name of a file that will hold  the  contents
       of  the specified log file.  Specifies that the last active record in the log file--the end of the log file--is to be displayed.  Specifies
       that all subtransactions of the parent transaction are to be followed.  Specifies that the first active record in the log  file--the  start
       of the log file--is to be displayed.  Verbose.  Display all the data in a specified log, page, or record.

OPERANDS

       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: Specify
       the -F option to force the utility to interpret the name you supply as a file name.  Specifies an AdvFS file  domain  using  the  following
       format:	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.  Specifies an AdvFS volume using the following format: 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 spe-
       cial file.

	      Alternatively, specify the volume by using arguments for its domain, domain_id, and its volume index number,  volume_index.   Speci-
	      fies the name of a file that contains the output from this utility.  Specifies the file page number of a file.  Specifies the offset
	      relative to the start or the end of the active region in the log file.  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 Kbyte 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  meta-
       data  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 before or after the start or the end of the active log.  For example, to dis-
       play 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 fol-
       lowing 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.  Note that 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 transac-
       tion by specifying a record and the -f option.

       Specify one particular log record and specify 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 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.  You 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  con-
       tradictory 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 run-
       ning. 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

       Specifies the command path.  Specifies the volumes in the domain.

SEE ALSO

       Commands: nvbmtpg(8), nvfragpg(8), tag2name(8), vfilepg(8), vsbmpg(8)

       Files: advfs(4)

																	nvlogpg(8)