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Creating multi-mirror snapshots

To make Database Snapshots highly available, the snapped snapshot volume should contain more than one mirror. This makes the snapshot volumes available even if one of the mirrors gets disabled. Snapshot volumes can be mounted and the entire database snapshot is usable even if one of the mirror gets disabled. The multi-mirror snapshots are enabled via SNAPSHOT_MIRROR=<n> in the snapplan.

  Note   There are no changes to the Command Line usage or arguments for the Flashsnap tools.

  Note   Before taking the snapshot, make sure all tagged snapshot mirrors are in SNAPDONE state.

The following sample explains the setup and the procedure for taking multi-mirror snapshots:

1. Add the second mirror and DCO log. When allocating storage for the second mirror and DCO logs, make sure the snap volumes are splittable. If snap volumes are not splittable, dbed_vmchecksnap fails with appropriate errors.

   Tag the newly added mirror with the same tag as that of the first mirror.

   Assume that the volume has fastresync = on, has dcolog = on, and already has one SNAPDONE mirror and is tagged with dbed_flashsnap.

# vxsnap -g dg_a addmir dg_a_vol1 alloc=dg_a03

# vxedit -g dg_a set putil2=dbed_flashsnap dg_a_vol1-03

2. AddSNAPSHOT_MIRRORkeyword to the snapplan.Here is a sample snapplan.

SNAPSHOT_VERSION=5.0

PRIMARY_HOST=host1

SECONDARY_HOST=host1

PRIMARY_DG=PRODdg

SNAPSHOT_DG=SNAP_PRODdg

ORACLE_SID=PROD

ARCHIVELOG_DEST=/prod_ar

SNAPSHOT_ARCHIVE_LOG=yes

SNAPSHOT_MODE=online

SNAPSHOT_PLAN_FOR=database

SNAPSHOT_PLEX_TAG=dbed_flashsnap

SNAPSHOT_VOL_PREFIX=SNAP_

ALLOW_REVERSE_RESYNC=no

SNAPSHOT_MIRROR=2

Establishing a mandatory archive destination

When cloning a database using Database FlashSnap, the Oracle database must have at least one mandatory archive destination.

See Cloning a database (dbed_vmclonedb)

If no mandatory archive destination is set, dbed_vmchecksnap results in this error message:

SFORA dbed_vmchecksnap ERROR V-81-5677 Could not find a mandatory, primary and valid archive destination for database PROD.

Please review the LOG_ARCHIVE_DEST_n parameters and check v$archive_dest.

This example shows how to establish a mandatory archive destination using SQL*Plus:

alter system set log_archive_dest_1 = 'LOCATION=/ora_mnt/oracle/oradata/PROD/archivelogs MANDATORY [REOPEN]' [scope=both];

For more information about Oracle parameters for archiving redo logs, see your Oracle documentation.