StorageTek Host Software Component 6 User Manual

1st ed., 6/30/04 - 312579601

The precedence of VOLATTR and TAPEREQ statements depends on whether the request 
is for a specific or nonspecific volume. 

For a specific volume request, VOLATTR information overrides TAPEREQ information 
provided that the VOLATTR statements supply both media type and recording technique. 

For example, if the TAPEREQ statement specifies MEDia(ECART) RECtech(36track) 
and the VOLATTR statement specifies MEDia(Standard) but does not specify RECtech, 
the result is MEDia(Standard) from the VOLATTR statement and RECtech(36track) from 
the TAPEREQ statement. 

If the VOLATTR statement provides a value for RECtech, then that recording technique is 
used, but the TAPEREQ statement can ‘‘refine’’ the RECtech value. For example, the 
VOLATTR statement specifies a recording technique of 36track, and the TAPEREQ 
statement specifies 36Btrack, then 36Btrack is used. 

Note: When mixing media types, the user must define VOLATTR statements because 
scratch counts are determined entirely from VOLATTR information.Accurately defined 
VOLATTR statements are critical for correct processing of nonspecific volume requests.

The HSC analyzes the TAPEREQ information to determine the required media type and 
recording technique, and then tries to locate available scratch volumes in the library that 
match these values. If no matching scratch volumes are available, HSC rejects the request. 

Scratch volumes are segregated by means of scratch subpooling with VOLATTR 
statements. Assuming that requested subpool definitions do not conflict with the 
applicable VOLATTR statements, the HSC provides the following services to satisfy a 
request: 

• If scratch volumes are segregated by defining subpools and specifying VOLATTR 

statements, the HSC ensures that a volume with the appropriate media type is 
selected from the correct subpool. 

• If scratch volumes are segregated only by defining subpools, the HSC selects a 

standard cartridge from the correct subpool. A standard cartridge is selected because 
this is the default when VOLATTR statements are not defined. 

• If volumes are segregated only by specifying VOLATTR statements, the HSC 

ensures that a volume with the appropriate media type is selected.