SQL/MP Installation and Management Guide

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Performing Recovery Operations

HP NonStop SQL/MP Installation and Management Guide—523353-004

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Managing Shadow Disk Labels

Shadow labels are the internal labels created by the disk process when SQL objects

are dropped within a transaction. Normally, these labels are deleted soon after the

transaction completes. In some situations, however, especially during abnormal

processing or a system crash, these labels are not deleted until file recovery is

performed.

Usually, shadow labels do not cause any problems on the system, but if users issue

subsequent CREATE statements to create objects with the same file name as the

shadowed label, the create operation fails.

You can remove shadow labels with the SHADOWSONLY option of the PURGE utility.

Identifying Shadow Labels

You might see shadow labels for a short period of time following the DROP or PURGE

command; this is normal. Sometimes shadow labels are left on the system.

You can detect shadow labels by using either the DSAP or FILEINFO commands. You

must run the command on all the volumes or qualified file-set lists that might have

resident SQL labels to check that no shadow labels exist.

DSAP reports the message “(SQL Shadow)” after the file name to indicate the file label

is shadow only. DSAP might also indicate that the file has doubly allocated extents.

These shadow labels might be the result of active DROP or PURGE commands that

have not removed the shadow label. The extents are allocated until the shadow label is

dropped or removed.

This command illustrates using DSAP on volume $VOL1:

51> DSAP $VOL1 DETAIL SQL

FILEINFO indicates shadow labels by displaying an S in the file type field of the report.

If you request a detailed FILEINFO display, SQL SHADOW LABEL appears in the line

describing file type; however, some other information is not available, such as key

information and index information.

These commands use FILEINFO to detect shadow labels:

>> FILEINFO *.*.*, SHADOWS

>> FILEINFO *.*.*, DETAIL SHADOWS

Removing Shadow Labels

You can remove shadow labels from the system with either the PURGE or CLEANUP

utility. The SHADOWSONLY option of these utilities enables or disables the purging of

shadow labels.

The SHADOWSONLY option is like a toggle. If you specify SHADOWSONLY, only

shadow labels in the file set list are purged; other files in the file set list are not