| Document revision date: 30 March 2001 | |
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For SCSI devices that support READL and WRITEL operations, SDA displays a Characteristics field that does not contain the NOFE flag, similar to the following example:
SDA> SHOW DEVICE DKA200:
I/O data structures
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COLOR$DKA200 Generic_DK UCB address: 806EEAF0
Device status: 00021810 online,valid,unload,lcl_valid
Characteristics: 1C4D4008 dir,fod,shr,avl,mnt,elg,idv,odv,rnd
01010281 clu,srv,nnm,scsi
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The Characteristics field does not show a NOFE bit set; therefore,
device DKA200 can support shadowing data repair.
1.8.5 Obtaining Shadow Set Information With F$GETDVI
The F$GETDVI lexical function provides another method for obtaining information about devices mounted in shadow sets. Using F$GETDVI, you can obtain general device and volume information and specific information about the shadow set status of the device or volume. For example, you can determine the following types of information:
You can use the F$GETDVI lexical function interactively at the DCL command level or in a DCL command procedure. You can also use the $GETDVI system service with volume shadowing (see <REFERENCE>(sysgetdvi_sect)).
The format for the F$GETDVI lexical function is as follows:
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F$GETDVI (device-name,item) |
You supply two arguments to the F$GETDVI lexical function: a physical device name and the name of an item that specifies the type of information you want to obtain.
If you use the file-system-related item codes with the $GETDVI system service to obtain meaningful system information (such as FREEBLOCK information) for a shadow set, you should specify the virtual unit name with the $GETDVI service. If you specify the device name of one of the shadow set members, the $GETDVI service returns a value of 0. |
The OpenVMS DCL Dictionary contains a large list of item codes that you can supply as an argument to F$GETDVI. Table 1-4 lists the items specific to volume shadowing that you can supply as arguments to the F$GETDVI lexical function. The table lists the type of information returned by each item and the data types of the return values.
| Item | Return Type |
Information Returned |
|---|---|---|
| SHDW_CATCHUP_COPYING | String | Returns TRUE or FALSE to indicate whether the device is a member that is the target of a copy operation. |
| SHDW_MASTER | String | Returns TRUE or FALSE to indicate whether the device is a virtual unit. |
| SHDW_MASTER_NAME | String | Returns the name of the virtual unit that represents the shadow set of which the specified device is a member. F$GETDVI returns a null string if the specified device is not a member or is, itself, a virtual unit. |
| SHDW_MEMBER | String | Returns TRUE or FALSE to indicate whether the device is a shadow set member. |
| SHDW_MERGE_COPYING | String | Returns TRUE or FALSE to indicate whether the device is a member that is a merge member of the shadow set. |
| SHDW_NEXT_MBR_NAME | String |
Returns the device name of the next member in the shadow set. If you
specify a virtual unit, F$GETDVI returns the device name of a member of
the shadow set. If you specify the name of a shadow set member with the
device name and item arguments, F$GETDVI returns the name of the
"next" member or a null string if there are no more members.
To determine all the members of a shadow set, first specify the virtual unit to F$GETDVI; on subsequent calls, specify the member name returned by the previous F$GETDVI call until it has finished, when it returns a null member name. |
To check a device for possible shadow set membership, you could include the following DCL command in a command procedure:
$ IF F$GETDVI("WRKD$:","SHDW_MEMBER") THEN GOTO SHADOW_MEMBER
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If WRKD$ (a logical name for a disk) is a shadow set member, then F$GETDVI returns the string TRUE and directs the procedure to the volume labeled SHADOW_MEMBER.
See the OpenVMS DCL Dictionary for additional information about the F$GETDVI lexical function.
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