StorageTek 6 manual Precedence of VOLATTR and TAPEREQ Statements, Specific Volume Requests

Precedence of VOLATTR and TAPEREQ Statements

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

Specific Volume Requests

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.

Nonspecific Volume Requests

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 Selection

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.

30VM/HSC 6.0 System Programmer’s Guide

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