Veritas™ File System 5.0.1 Programmer's Reference Guide

VX_FCL_DATA_EXTNDWRITE
VX_FCL_DATA_OVERWRITE
The following shows a typical sequence of FCL records written to the log, when
file a is renamed to b and both files are in the file system:
VX FCL_UNLINK (for file b, if it already exists)
VX_FCL_RENAME (for a rename from a to b)
File Change Log tunables
You can set four FCL tunable parameters using the vxtunefs command.
See the vxtunefs(1M) manual page.
The following are the four available FCL tunable parameters:
Specifies the duration in seconds that FCL records stay in the FCL file
before they can be purged. The first records to be purged are the oldest
ones, which are located at the beginning of the file. Additionally,
records at the beginning of the file can be purged if the allocation to
the FCL file exceeds fcl_maxalloc bytes. The default value is “0”.
Note that fcl_keeptime takes precedence over fcl_maxalloc. No
hole is punched if the FCL file exceeds fcl_maxalloc bytes and the
life of the oldest record has not reached fcl_keeptime seconds.
Tuning recommendation: The fcl_keeptime tunable parameter
needs to be tuned only when the administrator wants to ensure that
records are kept in the FCL for fcl_keeptime length of time. The
fcl_keeptime parameter should be set to any value greater than
the time between FCL scans. For example, if the FCL is scanned every
24 hours, fcl_keeptime could be set to 25 hours. This prevents FCL
records from being purged before they are read and processed.
fcl_keeptime
Specifies the maximum amount of space in bytes to be allocated to
the FCL file. When the space allocated exceeds fcl_maxalloc, a hole
is punched at the beginning of the file. As a result, records are purged
and the first valid offset is updated in the FCL superblock. The
minimum value of fcl_maxalloc is 4MB. The default value is
fs_size/33.
fcl_maxalloc
25File Change Log
File Change Log tunables