Virtual tape media

You can use virtual tape devices to save data directly to system disk units for convenience, flexibility, and in some cases improved performance. These scenarios will give you some examples of ways that you can utilize virtual tape in your save environment.

Virtual tape is beneficial for unattended saves because it eliminates media errors that could halt an unattended save. If you do not allocate enough space in the virtual volumes within the image catalog to save the intended information, virtual tape will use the auto-generate feature to create additional virtual tape volumes.

Ability to duplicate to physical media

When a save is complete to a virtual tape volume, you can duplicate the data to physical media at any time and not interfere with system operations. You also have the capability to send the stream files from the virtual tape save to another system via FTP SSL. If you have multiple systems, your strategy could be to save each system to virtual tape. Then, FTP the stream files to a single system where the duplication to the physical media could take place.

In a disaster recovery situation have physical media to perform your recovery. If you are saving to virtual tape as part of your disaster recovery strategy, duplicate your virtual saves to physical media.

Save to virtual tape

Perform the following steps to save data to virtual tape media.

Ensure that the system has enough disk space to hold all the virtual images you are going to create for your save operation.

Create a virtual tape device.

CRTDEVTAP DEVD(virtual-device-name) RSRCNAME(*VRT) ONLINE(*YES) +
TEXT(text-description)

Vary on the virtual tape device.

VRYCFG CFGOBJ(virtual-device-name) CFGTYPE(*DEV) STATUS(*ON)

Create an image catalog for your save operation.

CRTIMGCLG IMGCLG(catalog-name) DIR(catalog-path) CRTDIR(*YES) +
TEXT(catalog-descritpion) TYPE(*TAP)

Add new image catalog entries with a total capacity large enough for the amount of data that you intend to save. If you plan to duplicate image catalogs to physical media, then ensure you select a density that has a compatible block size for the device that will be holding your data. The following command will create a new standard labeled virtual tape volume with a maximum size of 10GB that will be compatible for duplication to a physical tape device that supports a 256KB maximum block size. The full 10GB of storage will be allocated at create time.
```
ADDIMGCLGE IMGCLG(catalog-name) FROMFILE(*NEW) TOFILE(VOL001) +
IMGSIZ(10000) TEXT(text-description) ALCSTG(*IMGSIZ) 
VOLNAM(VOL001) VOLTYP(*SL) DENSITY(*VRT256K)
```
Repeat this step for the number of desired images. You should add the images in the same order as you plan to restore from them. The virtual images provide spanning capability, with sequence numbers continuing from one volume to the next. The image size can be as small as 48MB or as large as 1,000,00MB. If you do not want to pre-allocate the storage you can use ALCSTG(*MIN) and the storage will only be allocated as it is used for the save.
Load the image catalog. This step associates the virtual tape device to the image catalog. Only one image catalog at a time can be associated with a specific virtual tape device.
```
LODIMGCLG IMGCLG(catalog-name) DEV(virtual-device-name) OPTION(*LOAD)
```
Run a save command listing the virtual tape device in the DEV parameter. Virtual tape devices operate similar to tape media library devices so entering the volume names in the volume parameter automatically mounts the volumes.

Exclude virtual images from a full save

After you create virtual tape images, they will automatically be included when you perform a full system save using GO SAVE Option 21. The virtual tape images could significantly increase the time it takes to complete the Option 21 save operation, even if the image catalog entries do not contain data. If you want to exclude the virtual images from a full system save, use one of the following strategies:

Use the Change Attribute (CHGATR) command to mark the image catalog directory as non-saveable. For example:
```
CHGATR OBJ('/Catalog-Path') ATR(*ALWSAV) VALUE(*NO) 
```
Use the Load Image Catalog (LODIMGCLG) command to make the image catalog ready. Image catalogs with a ready status will be omitted from the save.
In an attended save, you can specify to omit the image catalog directories on the Save Object (SAV) command.

Parent topic:

Choosing your save media

Related information
Virtual Tape