HP 3000 Manuals HP 3000 Manuals
Silhouette A.01.00
by Gary Alvord--Commercial Systems Division
Silhouette has been enhanced to use Network Inter-Process Communication
(NetIPC) and Remote Process Management (RPM) services of NS/3000. Built
into the Silhouette system startup routine is the ability to determine
which data communication service to use: DS/3000 Program-to-Program (DS
PTOP) for earlier data communication systems or NS/3000 NetIPC and RPM
for newer systems using LAN/3000. One common version of Silhouette is
required for all systems in the Silhouette network.
NEW SECONDARY SYSTEM FAILURE PROTECTION FEATURE
Enabling the Secondary database for rollback recovery will invoke a new
feature to help protect the integrity of the Secondary database after a
system software failure. The purpose of enabling the Secondary database
for rollback recovery is to ensure physical I/O by TurboIMAGE to the
databases. If the Silhouette software has determined that rollback is
enabled, Silhouette will also ensure that physical I/O is performed for
all writes to the SAVE file. This method protects against Secondary
failures on MPE V/E systems (with disc caching enabled) and MPE XL
systems. The Secondary system must be recovered using a "warmstart" on
MPE V/E and "start recovery" on MPE XL for this feature to properly work.
Installation
* Shut Silhouette processing down and ensure there is no access to the
Secondary database.
:RUN SILMP.PUB.SYS << On the Primary System >>
>SYSTEM config
>STOP
:RUN DBUTIL.PUB.SYS << On the Secondary System >>
>>SHOW database USERS
>>EXIT
* On the Secondary system, build a logfile using Automatic CHANGELOG.
If there is currently a Silhouette logfile in this group be sure to
use a different name. Note that this logfile is a TurboIMAGE
byproduct from enabling rollback recovery for your database.
Inactive logfiles may be purged at the operator's convenience. To
help facilitate this, use the Automatic CHANGELOG.
:BUILD logfl001.group.account;CODE=LOG;DISC=10000,10,10
* Obtain a logid.
:GETLOG logproc;LOG=logfl001.group.account,DISC;AUTO
* Enable the Secondary database for rollback. This must be done for
all the databases listed in the configuration file. All databases in
the configuration file must have rollback enabled or this feature
will not be invoked.
:RUN DBUTIL.PUB.SYS
>>ENABLE databasename FOR ROLLBACK
>>EXIT
* Start Silhouette.
:RUN SILMP.PUB.SYS
>SYSTEM config
>START
When Silhouette is restarted, the Recovery Process (SILRP) will
determine whether ROLLBACK is enabled on the Secondary database by
checking the root file. If ROLLBACK is enabled, all I/O to the SAVE
file will be guaranteed to complete. The following message should
appear in the Recovery Process job listing spoolfile indicating that
ROLLBACK is enabled.
"DBs enabled with ROLLBACK - physical I/O to SAVE"
Recovery
Previously, if the Silhouette Recovery Process was updating a database at
the same moment as a system software failure there was no guarantee of
the integrity of the Secondary database. The SAVE file may have also
lost some transaction counts which could leave this file out of
synchronization with the database(s). Enabling ROLLBACK on the Secondary
database will now guarantee logical integrity of Secondary databases and
synchronization with the recovery-SAVE files. With this new feature,
after recovering the Secondary system using a "warmstart" for MPE V/E and
"start recovery" for MPE XL, you simply restart Silhouette and the
software will resume duplicating from the point of the failure.
NEW SWITCH COMMAND OPTIONS
New options for the SWITCH command have been implemented to provide the
same flexibility as the RECOVER command. An option such as norollback on
a SWITCH can be particularly useful if a customer has their own utility
to rollback incomplete transactions. The syntax and description of these
options is described on the following page.
Syntax
>SWITCH [,optionword]
Parameters
optionword This specifies the RECOVER option. The options are:
report The report option word tells the
Silhouette software to read the logfile
records and produce a normal recovery
report without making any changes to
the database. In other words, this
option generates a report describing
what the database would look like if a
normal recovery were to be performed.
norollback The norollback option word tells the
Silhouette system to perform a normal
recovery without removing incomplete
transactions from the database. A
database recovered in this fashion may
be internally inconsistent but it is
guaranteed to contain every transaction
which was applied to the database
before the system failed.
norollfwd The norollfwd option word tells the
Silhouette software to process the
logfile records without applying them
to the database. Incomplete
transactions will be removed as they
are in a normal recovery. This option
is used then to clean up a logfile
which is known to contain incomplete
transactions.
Discussion
If the SWITCH command is issued with no option word, any transactions
that have been sent to the Secondary system but not yet processed will be
processed. The database will then be brought into a consistent state
with incomplete transactions removed from the database as required. A
report will be printed showing the last complete transaction for each
user of the database and any incomplete transactions which the database
may have contained before their removal by the Silhouette software. Once
the SWITCH command has been issued, the databases are no longer
synchronized and may no longer be used for shadowing until the database
is copied over to the new Primary system.