**************************************************
* *
* This tool is now obsolete. You should *
* be using the system support directly or *
* the SAVACT tool. *
* *
**************************************************
The SAVWHLACT command allows a data base file to be saved while it is
active. Being active means that the file is open for update and one
or more programs are making changes while the save occurs. The
companion command RSTWHLACT does a restore from the copy made by
SAVWHLACT. Then it applies changes which occurred during the copy.
These commands are specifically designed for those environments where
the file should be available for update around the clock. When this
type of situation exists, the installation typically requires a
window of time in the wee hours of the morning to be used for backup
when users must signoff or be kept out of an application area. The
SAVWHLACT command allows you to get rid of the window and makes the
file available all of the time.
The file being saved must be journaled. The journal changes are used
to bring the file back to a proper state. It is possible to start
journaling just prior to SAVWHLACT and then to end journaling after
the command completes. However, the start and end journaling
commands require the file to be exclusively allocated. See the later
comments about temporarily journaling the file.
The SAVWHLACT command does not save the file offline or to a save
file. It only makes a copy of the file that along with the journal
receiver can be saved to produce an offline backup of the file.
To use the SAVWHLACT command you must create a backup library where
the file/members can be saved (copied) to. The file/members must
exist prior to executing the command.
This library must also contains the files WHLACTP and WHLACTL which
describe the files being used. The WHLACTP and WHLACTL files must be
created by the CRTWHLACT command.
A typical use of the SAVWHLACT command would be:
SAVWHLACT FILE((FILEA)(FILEB)) BACKUPLIB(BACKUP)
The command copies the data from the files specified to the
corresponding file/members in the backup library. The WHLACTP file
is updated to describe the files copied and the beginning and ending
journal sequence numbers. These sequence numbers are used by the
RSTWHLACT command. The corresponding RST command would be:
RSTWHLACT FILE((FILEA)(FILEB)) BACKUPLIB(BACKUP)
The RST command copies the file back and then uses the APYJRNCHG
command to bring the files back to the same point. While the RST
command is executing, the file is exclusively locked.
When the SAVWHLACT command is executed, the current journal sequence
is saved just prior to copying each file. When the copy is complete,
the current journal sequence number is also saved for informational
purposes. When the command completes, the current journal sequence
number is also saved. This last sequence number denotes the common
synch point to recover all files to.
When the RSTWHLACT command is executed, the copy back is done and
then the APYJRNCHG command is issued from the sequence number where
the original copy was started from, to the command completion
sequence number. This has the effect of bringing all files specified
on the RST back to a common synch point (This assumes that all files
restored with the same RST command were saved with the same SAV
command). The intent of this approach is to provide for a common
restart point if it is necessary to recover the files.
The backup copy made is done by CPYF with COMPRESS(*NO). This causes
an exact match of the file in terms of relative record numbers. Any
deleted records in the FROM file become deleted records in the TO
file. This ensures that the proper relative record numbers can be
used by the APYJRNCHG command.
During the execution of the APYJRNCHG command, some errors may occur.
For example, if a record is deleted after the copy starts, but before
the deleted record number is accessed by the copy, a deleted record
will appear in the backup version. When the APYJRNCHG command is
executed, the journal entry for the delete will attempt to delete a
deleted record which will cause an error. The RST command assumes
that any such errors which occur during the from/to sequence numbers
specified will be ignored. The APY command is restarted at the next
sequence number.
Rebuilding of access paths
--------------------------
When the RSTWHLACT command executes, any access paths on the original
file will be rebuilt. This is a consideration in the use of this
approach on very large files with many access paths.
For example, when a system save command executes, you have an option
to save access paths. This is generally desirable to reduce the
amount of time if a restore is needed. Because CPYF is being used
with SAVWHLACT, the access path of the original file cannot be saved.
If the benefits of saving while active are significant, it may still
be a good choice to use the function on large files if the number of
restores expected is small.
Differences with the SAV command SAVWHLACT function
---------------------------------------------------
The following reviews the major differences:
** The TAA Tool only supports data base physical files.
** The TAA Tool requires the files to be journaled.
** The TAA Tool does not provide for commitment control
boundaries.
** The TAA Tool will rebuild access paths when the restore
function is used. The SAV commands allow a saving of the
access paths so rebuilding can be avoided on a restore.
** The system function causes a seize (everyone using a library
is locked out until the seize completes). The TAA Tool does
not lock out anyone.
** The system function supports commitment control, but requires
users to be at a quiet point before the save can begin. In
extreme instances this can be a long time or may never occur
(the system function supports a timeout value). A user
completing a commitment control boundary will be locked out
until all users have reached a quiet point or the timeout
occurs.
** The TAA Tool is not library sensitive. The files can be
anywhere and recovery should occur normally.
CRTWHLACT command parameters *CMD
----------------------------
LIB The library to create the files in.
SRCLIB The source library to use for the QATTDDS file. The
default is *TAAARC which means to use the source in
the TAA Archive.
SAVWHLACT command parameters *CMD
----------------------------
FILE This is a list of up to 40 file/members that may be
specified. Note that if a multi-member file exists,
you must name each member. The file/members must
exist in the backup library. Each file named must
be journaled and all files on a given command must
be journaled to the same journal. Each list is made
up of the following elements:
FILE The file name to be saved.
LIB The library containing the file. The default
is *LIBL.
MBR The member of the file. The default is *FIRST.
BACKUPLIB The backup library to be used. This library must
contain the file/member specified on the FILE
parameter and the files WHLACTP and WHLACTL
described in the implementation steps.
DLTDAYS This parameter provides for automatic housecleaning
of the WHLACTP file. The default is 30 meaning that
any entries made to the file that are 30 days old or
older will be deleted.
RSTWHLACT command parameters *CMD
----------------------------
FILE This is a list of up to 40 file/members that may be
specified. Note that if a multi-member file exists,
you must name each member. The file/members will be
allocated to *EXCL during the command execution.
Each list is made up of the following elements:
FILE The file name to be restored.
LIB The library containing the file. The default
is *LIBL.
MBR The member of the file. The default is *FIRST.
BACKUPLIB The backup library to be used. This library must
contain the file/member specified on the FILE
parameter and the files WHLACTP and WHLACTL used by
SAVWHLACT.
Parameter notes
---------------
Note that the default for both commands is MBR(*FIRST). The WHLACTP
file will describe the data by this name. If MBR(*FIRST) is
specified on SAVWHLACT, it must also be specified on RSTWHLACT. The
file WHLACTP contains both the MBR name specified on the command
(i.e. it could be *FIRST) and the actual member used. It would be
possible to modify the information in the WHLACTP file prior to
executing the RSTWHLACT command if *FIRST is no longer the proper
value.
Recovery steps
--------------
If the file to be recovered is still on the system, is not damaged
and is being journaled, the RSTWHLACT command can be issued without
performing a restore or CLRPFM.
If the file is not being journaled, but is the same file that
SAVWHLACT was executed against, you may restart journaling to the
same journal and have RSTWHLACT operate successfully.
If the file has been deleted, you must restore the original file
before executing the RSTWHLACT command. The file you restore must
have been saved while the file was being journaled (i.e. after the
STRJRNPF command). This is a standard restriction with the APYJRNCHG
command that it will only operate against the file that was
originally journaled.
When journaling is started, an internal journal ID is assigned to the
file that must match a similar entry in the journal in order to
execute the APYJRNCHG command. The journal ID is saved with the file
and reused on a restore. The journal ID assigned is based on an
algorithm including such things as the machine serial number and a
consecutive number assigned for each journal, etc. If the file has
not been deleted and the file was previously assigned a journal ID,
it is reused. Therefore, if the same file still exists but
journaling is started, ended and then restarted, the same journal ID
will be used and the APY command can be used successfully.
If a mismatch occurs, you can still recover the file by doing the
following:
1. Use CPYF to restore the backup version from the backup
library. Specify COMPRESS(*NO) MBROPT(*REPLACE) and
FROMRCD(1).
2. Display the contents of the WHLACTP file to determine the
starting and ending journal sequence numbers to be used for
the file/member desired. Use these sequence numbers to build
an output file with the DSPJRN command.
3. Have a user application apply the journal entries for the
specific file. An example of such a program and an approach
which can be used is the APYUSRCHG TAA Tool.
In general, it would be a good practice to be ready to execute a
command like APYUSRCHG in case of any problems that might occur.
Audit trail
-----------
The WHLACTP file contains several fields that may be useful for audit
trail purposes. You will need to write a display or print program
for this file or use query.
Journal entries are also made during the execution of the SAV and RST
commands to provide a better audit trail. The SNDJRNE TYPE codes are
as follows:
SS SAVWHLACT started
SC CPYF started
SE CPYF ended
SN SAVWHLACT normal completion
RS RSTWHLACT started
RC CPYF back started
RN RSTWHLACT normal completion
Temporarily journaling the files
--------------------------------
When the SAVWHLACT command executes, it ensures the file is being
journaled. It is possible to specify STRJRNPF just prior to
executing the SAVWHLACT command and then ENDJRNPF after the command
completes. However, both commands require exclusive use of the file.
The RSTWHLACT command can be used to recover the file if the file has
not been recreated since journaling ended. The file must be actively
being journaled in order to execute RSTWHLACT.
Year 200 Implications
---------------------
SAVWHLACT cannot begin in one century and end in another. Because
the format of the journal entries used have only 6 character dates, a
error message will be sent if the century boundary is crossed. Note
that this is only a restriction if the command started before
midnight of 12/31/99 and ended in the following year.
RSTWHLACT can be used to restore from a save which occurred in a
previous century.
Prerequisites
-------------
The following TAA Tools must be on your system:
ADDDAT Add date
EXTLST Extract list
RTVPFA Retrieve physical file attributes
SNDCOMPMSG Send completion message
SNDESCMSG Send escape message
SNDSTSMSG Send status message
TAAARC TAA Archive
Implementation
--------------
The tool is ready to use, but you must first create the files used by
the tool (WHLACTP and WHLACTL) into the same library where the backup
files will be placed. Use the command:
CRTWHLACT LIB(xxx)
Objects used by the tool
------------------------
Object Type Attribute Src member Src file
------ ----- --------- ---------- -----------
* WHLACTP *FILE PF TAASAVEP QATTDDS
* WHLACTL *FILE LF TAASAVEL QATTDDS
SAVWHLACT *CMD TAASAVE QATTCMD
RSTWHLACT *CMD TAASAVE2 QATTCMD
CRTWHLACT *CMD TAASAVE3 QATTCMD
TAASAVEC *PGM CLP TAASAVEC QATTCL
TAASAVEC2 *PGM CLP TAASAVEC2 QATTCL
TAASAVEC3 *PGM CLP TAASAVEC3 QATTCL
TAASAVER *PGM RPG TAASAVER QATTRPG
* These files will exist in the library specified on CRTWHLACT.
Structure
---------
CRTWHLACT
TAASAVEC3 CL pgm
SAVWHLACT
TAASAVE CL pgm
TAASAVER RPG pgm
RSTWHLACT
TAASAVE2 CL pgm
TAASAVER RPG pgm
Backup library implementation
-----------------------------
1. Create a library for your backup files or select one of your
existing libraries to be used for backup. The library cannot
contain any of the file/members that you intend to specify on
SAVWHLACT. You may have multiple libraries used for
SAVWHLACT, but each must have the WHLACTP and WHLACTL files
specified in the next steps.
Use the command CRTWHLACT to create WHLACTP and WHLACTL files
in the same library.
2. Create the file/members in your backup library that you want
to backup. The TAA Tool DUPFILFMT would be a good choice to
create a duplicate file. You will normally not want the
backup file to be keyed as this will slow down the time it
takes to do the backup because an access path must be built.
The DUPFILFMT command creates a member of the same name as the
file. The record capacity of the current file is used as the
first element of the SIZE parameter for the new file. Ten
percent of the record capacity is used as the size of the
increment and the number of increments is set to 3.
You are now ready to execute the SAVWHLACT command.
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