JAL: copied from m204stage

2016-11-04T19:56:13Z

copied from m204stage

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<var class="product">Fast/Backup</var> is a plug-compatible replacement for the <var>[[DUMP command|DUMP]]</var> and <var>[[RESTORE command|RESTORE]]</var> commands provided with <var class="product">Model 204</var>.
The <var class="product">Fast/Backup</var> add-on combines the functional
appeal of the <var class="product">Model 204</var> backup program with the speed of a system backup utility such as IBM's DF/DSS®.

As of Model 204 7.5, the <var class="product">Fast/Backup</var> modules are linked into the Online. If you are authorized to use <var class="product">Fast/Backup</var>, a <var class="product">Model </var> <var>DUMP</var> command invokes <var class="product">Fast/Backup</var>. If you are not so authorized, a <var>DUMP</var> command executes the standard <var class="product">Model 204</var> code for dumping a file. The same is true for <var>RESTORE</var>.

Prior to Model 204 7.5, <var class="product">Fast/Backup</var> was installed as part of the <var class="product">[[Sirius Mods]]</var>, and
no <var class="product">Sirius Mods</var> products were required to run <var class="product">Fast/Backup</var> other than itself.

==Using Fast/Backup under z/OS==
<var class="product">Fast/Backup</var> supports the same command structure as the <var class="product">Model 204</var> <var>DUMP</var> and <var>RESTORE</var> commands.
<var class="product">Fast/Backup</var> also provides the additional options described below in [[#Fast/Backup options|Fast/Backup options]].

<var class="product">Fast/Backup</var> acquires its own database buffers to avoid impacting <var class="product">Model&n|bsp;204</var> buffer pool performance.
The storage is acquired "above the line" in XA and ESA environments.

A special subtask is created for <var class="product">Fast/Backup</var> under z/OS to avoid delays in the Online environment due to tape volume mounts.

You can set the <var>[[DUMPTMIN parameter|DUMPTMIN]]</var> and <var>[[DUMPTMAX parameter|DUMPTMAX]]</var> parameters to optimize dumps in an updating environment.
Normally, updating transactions are delayed while second or subsequent tape volumes are mounted during a <var>DUMP</var>.
But <var class="product">Fast/Backup</var> writes updated pages to [[Using the system scratch file (CCATEMP)|CCATEMP]] while waiting for a volume mount.
This allows updating transactions to continue, since a pre-image page is immediately logged in CCATEMP.
As soon as the tape volume becomes available, the CCATEMP pages are written to it and freed.

<var>DUMPTMIN</var> sets the minimum number of CCATEMP pages that must be
available when <var class="product">Fast/Backup</var> requires one for pre-image logging.
<var>DUMPTMAX</var> sets the maximum number of pages a single <var>DUMP</var> can use.
You can set the <var>[[DUMPOPTS parameter|DUMPOPTS]]</var> flag to indicate the action to take if either of these page limits are violated:

<table class="thJustBold">
<tr class="head"><th>Flag</th><th>Action</th></tr>

<tr><th>X'00'</th>
<td>Wait. This causes the <var>DUMP</var> process to wait for the volume mount, which forces any updating transactions to wait also. </td></tr>

<tr><th>X'80'</th>
<td>Cancel. This terminates the <var>DUMP</var> immediately (any other dumps in progress continue). </td></tr>
</table>

<var class="product">Fast/Backup</var> automatically selects the best possible blocksize for the sequential data set.
Unless you have special restrictions or
considerations, do not code a <var>BLKSIZE</var> parameter on your DD statement or in your <var>ALLOCATE</var> command.

If, for any reason, you want to use standard Model 204 <var>DUMP</var> or <var>RESTORE</var> after
you have installed <var class="product">Fast/Backup</var>, you can do so by changing your <var>DUMP</var>
commands to <var>DUMPX</var>, and your <var>RESTORE</var> commands to <var>RESTOREX</var>.
These commands will invoke the standard <var>DUMP</var> and <var>RESTORE</var> functionality.

==Using Fast/Backup under CMS==
<var class="product">Fast/Backup</var> supports the same command structure as the <var class="product">Model 204</var> <var>DUMP</var> and <var>RESTORE</var> commands.
<var class="product">Fast/Backup</var> also provides the additional options described below in [[#Fast/Backup options|Fast/Backup options]].

<var class="product">Fast/Backup</var> acquires its own database buffers to avoid impacting <var class="product">Model 204</var> buffer pool performance.
The storage is acquired "above the line" in XA and ESA environments.

<var class="product">Fast/Backup</var> automatically selects the best possible blocksize for the sequential data set.
Unless you have special restrictions or considerations, do not code a <var>BLKSIZE</var> parameter on your DD statement or in your <var>ALLOCATE</var> command.

If, for any reason, you want to use standard CCA <var>DUMP</var> or <var>RESTORE</var> after
you've installed <var class="product">Fast/Backup</var>, you can do so by changing your <var>DUMP</var> commands to <var>DUMPX</var>, and your <var>RESTORE</var> commands to <var>RESTOREX</var>.
These commands will invoke the standard Model 204 commands.

Fast/Backup does not support <var>DUMP</var> or <var>RESTORE</var> for database files that reside on a CMS minidisk.
<var>DUMP</var> or <var>RESTORE</var> will revert to the standard Model 204 routines in this case.

==Performance considerations==
<var class="product">Fast/Backup</var> examines the device type and allocation of the database files before allocating I/O buffers.
<var class="product">Fast/Backup</var> attempts to use full cylinder I/O whenever possible, but any physical extents in the
database that are not cylinder aligned are read a track at a time.
Thus, you can maximize the performance of <var class="product">Fast/Backup</var> by ensuring that all database extents are allocated on cylinder boundaries.

<var class="product">Fast/Backup</var> reads and writes full tracks or cylinders in each database I/O operation, and requires two database I/O buffers to achieve best performance.
For 3380 devices this means that 1.3 Megabytes of
"above the line" storage is required for the database buffers.
You may need to adjust the size of your region before using <var class="product">Fast/Backup</var>.

The <var>NBUFF</var> option (described below in [[#Fast/Backup options|Fast/Backup options]]) sets the number of sequential I/O buffers for the <var>DUMP</var> or <var>RESTORE</var> operation.
You should set this value as high as possible to avoid sequential I/O bottlenecks, but this storage is allocated for use
by BSAM and must be "below the line," except in DF/SMS environments.
Setting <var>NBUFF</var> too high can induce high paging rates if
corresponding real storage is not available, or it can exhaust free storage in
the Online.

==Fast/Backup options==
<table class="thJustBold">
<tr><th>NBUFF</th>
<td><var>NBUFF</var> sets the number of sequential I/O buffers for <var>BACKUP</var> or <var>RESTORE</var>. Code the <var>NBUFF</var> keyword after the <var>DUMP</var> or <var>RESTORE</var> command. For example:
<p class="code">RESTORE 192 FROM TESTFILE NBUFF 50
</p>
Each buffer is equal in size to the blocksize of the sequential dataset.
Thus, if <var>NBUFF</var> is 20,and the sequential dataset blocksize is 30920 bytes, 618,400 bytes of storage will be needed for the sequential I/O buffers. <var>NBUFF</var> can be set to any number between 1 and 99 inclusive.
<p>
<var>NBUFF</var> is automatically set to: </p>
<p class="code"><i>pagesize</i> * 180 / <i>blocksize</i>
</p></td></tr>

<tr><th>DUMPTMIN</th>
<td>This user resettable system parameter sets the minimum number of free CCATEMP pages that must be available for <var>DUMP</var> to use for pre-imaging when waiting for second or subsequent tape volume mounts.</td></tr>

<tr><th>DUMPTMAX</th>
<td>This user resettable system parameter set the maximum number of CCATEMP pages any individual <var>DUMP</var> can use.</td></tr>

<tr><th>DUMPOPTS</th>
<td>This user resettable system parameter sets system-wide <var>DUMP</var> options.
<table>
<tr><th>X'00'</th>
<td>Indicates that if the <var>DUMPTMIN</var> or <var>DUMPTMAX</var> values are violated, dumps should wait for tapemounts without using CCATEMP pages. This will force updating transactions to wait also.</td></tr>

<tr><th>X'80'</th>
<td>Indicates that dumps should be canceled if either <var>DUMPTMAX</var> or <var>DUMPTMIN</var> limits are violated.</td></tr>
</table></td></tr>
</table>

Fast/Backup - Revision history

JAL: copied from m204stage