Request Volume Element Address - X'B5'

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For the tape library, the Request Volume Element Address command transfers the results of a Send Volume Tag command. Multiple Request Volume Element Address commands can be used to retrieve the results of a single Send Volume Tag command with the translate option. Table 1 shows the command format.

Table 1. Request Volume Element Address Command
Byte Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0 Operation Code (X'B5')
1 Reserved Voltag Element Type Code
2-3 Element Address
4-5 Number of Elements to Report
6 Reserved
7-9 Allocation Length
10 Reserved
11 Control

The following tape library-specific behaviors apply:

Element Type Code acts as a filter similar to (Minimum) Element Address, which, if the criteria are met, advances the most recent element address reported. Once information for an element address is reported, only higher element addresses are reported by subsequent Request Volume Element Address commands. Even if it means that some Send Volume Tag element list matches are skipped and never reported. If the criteria are not met based on the Element Type Code or Element Address (and there are still element addresses to be reported), this command responds with an empty volume element address header. However, the most recent element address that was reported is not advanced and the element list is not to be considered reported completely.

Table 2 shows the volume element address header format.

Table 2. Volume Element Address Header
Byte Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0-1 First Element Address Reported
2-3 Number of Elements Reported
4 Reserved Send Action Code
5-7 Byte Count of Report Available (all pages, x - 7)
8-x Element status page(s)

If a Request Volume Element Address command is received and no prior Send Volume Tag command was executed or the element list was reported completely for the most recently successful Send Volume Tag command, the library returns command response data that consists of only the volume element address header, with First Element Address Reported set to X'0000', Number of Elements Reported set to X'0000', and Byte Count of Report Available set to X'000000'.