Informing the IBM Community

Three reasons to look at INZTAP in a different light


The use of tape with IBM i is still truly ubiquitous, and yet virtually no one pays any attention to the way that the tapes are prepared.

Whether we are taking about GDPR secure data wipes, backup data integrity or identifying backup time, then INZTAP is a great tool to have in your tool kit.

Even those of you using software based High Available / Disaster Recovery tools, still tend to run daily backups to tape, even if they are on the target HA / DR server.

In short, these tapes form a key foundation to such backup routines and most people pay little to no attention to the preparation, integrity checking and deletion of this media.

So, here are three tips you might find useful, could save you money and will help you keep your data safe.

Wiping data from your tape

One of the most common misconceptions about the INZTAP command is that it wipes data from a tape.  By default, it does NO SUCH THING!

When you run an INZTAP, there is a parameter called CLEAR which by default is set to *NO, so when you run the command all that it wipes is the headers from the tape, not the data that sits beyond them.

This is why it only takes a few seconds to complete.

If you want to wipe a tape completely, then you need to specify *YES on the CLEAR parameter.  So, why don’t we specify CLEAR *YES on all INZTAP’s?  Well, the most compelling reason is that it takes several hours to wipe a typical tape.

What does the CLEAR *YES do? Well, put simply it writes zeros over the entire length of the tape, regardless of what data was previously written.

ProTip: When you need to wipe a tape for GDPR reasons, be sure to use CLEAR(*YES) but make sure you allow four hours for the INZTAP to complete. 

How can I tell if a tape is in good condition?

When tape media or it’s drive are past their prime, read / write errors tend to occur and in the world of IBM i these manifest themselves as rather generic failures called “Media Errors”.  As many of you will have learnt to your cost, Media Errors are a “pain in the backside”. They abnormally end a backup or restore operation and they seldom occur at the beginning of these often lengthy processes.

It’s not possible to know just by looking at a physical tape if it is past it’s prime, and the working life of a physical tape can vary dramatically depending on the environment in which it is both used and stored. 

So, if you have an important backup to run (perhaps a Save 21 or an ERP Year End) then it is worth checking the integrity of a tape in advance by performing a test operation that reads and writes to the entire tape.

Just in case the penny hasn’t dropped yet; using INZTAP with CLEAR(*YES) is ideal for this. By writing this null data to the entire tape, it allows you to test that the entire tape is good at the same time as preparing the tape for the backup.

What is on that tape?

When it comes to finding out what is on a tape, then there is no doubt that the display tape (DSPTAP) is the command that gives you the most information.  However, if you backup more than one LPAR or have multiple backups for a single LPAR then even DSPTAP can be ambiguous. 

Imagine that you have 10 different LPARS all that run the same application, so they have similar library, DLO and IFS names, then simply running a DSPTAP would not necessarily identify which LPAR the tape represented.

If you use the VOLUME and OWNER parameters, then this too can become self-evident.  

The VOLUME parameter is limited to 6 characters not ideal for disambiguating similar backups from different systems.

But when you add the New Owner parameter this gives you another 14 case sensitive characters.

So, in the example above we use the VOLUME parameter to identify the type of backup as DAILY and use the New Owner to Identify the system.

ProTip The VOLUME parameter is compulsory for IBM i backups to make sure tape is formatted with the Standard Labels needed for the standard IBM i Save and Restore commands

Bonus Tip for INZTAP use *CTGTYPE

One last bonus tip.  If you used Density(*CTGTYPE) then the INZTAP command will look at the type of tape loaded in the drive and pick the appropriate format for the type of tape you have loaded in the drive. This removes the need to know exactly what density of tape you have loaded in the drive, it just needs to be compatible with the drive.

i-UG goes Hybrid

Our next User Group Meeting will be in November and this time it’s a Hybrid. It will of course still be available Virtually via Zoom but also in person and the Mount Hotel in my home town of Wolverhampton. For more details check out

Hope to see you there.

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