SAP Note 18018 - Cold restore salvaging of unsaved logs

Symptom:

A cold restore, of all or individual DBSpaces, is to be carried out in the online mode (database is down) and as yet there are no saved logical log files on the system to be restored.

Cause and prerequisites

So that no transactions are lost, the logical log files that have not yet been saved must be saved as 'salvage logs' - before the physical Restore of the DBSpaces.

Solution

The procedure for saving the Salvage Logs is described below.
Requirements:

• The INFORMIX server is offline (stopsap), just like the SAP System

• The values of LTAPEDEV and TAPEDEV in the ONCONFIG file may not be set to '/dev/null' (UNIX) or 'NULL' (NT).

ONTAPE

When you start the Cold Restore, ontape determines that some logical logs are still available on your disk and requests the user to save these salvage logs before beginning the actual Cold Restore.

• To save the salvage logs an empty tape must be inserted in the drive requested by ontape.

• The salvage logs are saved as soon as the tape has been confirmed as inserted. If the saving has been completed, ontape reports which logs have been saved.

• Remove the tape with the salvage logs from the drive. We recommend labeling it with the logs saved on it.

Afterwards the normal restore can be continued. Follow the instructions by ontape.

The salvage logs are imported after the physical Restore during the logical restore, directly after the 'normal' logical logs have been imported.

ONARCHIVE

With ONARCHIVE, the process is a little different.
For the ondatartr command you must specify explicitly that the salvage logs are to be saved before the actual Restore begins.

• ondatartr 'RETRIEVE/DBSPACESET=<>
  /TAPE=()

/SALVAGELOGS='

The type of the drive to be used for the SALVAGELOGS must be identical to that for the level 0 archives to be reimported. That is to say, both must be either of type TAPE or DISK.

• Make the medium requested by ondatartr available (insert an emtpy tape and confirm the insertion).

• The tape is initialized. A volume is created for the salvage logs with the volume number 1 which is assigned to the volume set (VSET) ONDATARTRLOG.

• After this, the salvage logs are saved on this tape. When the saving is finished ondatartr reports which logs have been saved.

• Remove the tape with the salvage logs from the drive. We recommend that you label the tape with the logs saved on it.

The normal Restore can then be continued. Follow the instructions given by ondatartr.

The salvage logs are imported after the physical Restore, during the logical Restore and directly after the 'normal' logical logs have been imported.
ondatartr 'RETRIEVE/LOGFILE/TAPE=()'
ONBAR

For ON-Bar the salvage logs are saved implicitly, always before the beginning of the Cold Restore of the DBSpace.

The salvage logs are also imported implicitly as a part of the logical Restore.

As of online version 7.30 up to and including 7.31xC4, the implicit saving of the salvage logs can be deactivated, if the IECC is used. To do this, the value of LOG_BACKUP_MODE must be set to NONE in the ONCONFIG file before the beginning of the Cold Restore.


Setting the parameter to CONT (via IECC) has the same effect as setting the configuration parameter ALARMPROGRAM in ONCONFIG from $INFORMIXDIR/etc/log_full.sh (i.e. if IECC is not installed). ONCONFIG parameters LOG_BACKUP_MODE (via IECC) and ALARMPROGRAM turn the 'continuous log backup' on or off thus offering no functionality for a restore operation.

As from Release 7.31xC5, ISA is used instead of IECC. Salvaging the logs that had not been saved before can be prevented since version 7.31 using a two-step cold restore. Instead of a normal cold restore 'onbar -r' that implicitly salvages the logs, the 1st step should contain a physical cold restore 'onbar -r -p' which does NOT salvage the logs. The 2nd step contains a logical cold restore 'onbar -r -l'.
The following is recommended:

• Save emergency boot files,

• carry out a level-0 backup.
  

After the Restore

After the logical recovery the server is in the Quiescent mode.
onstat -

The Restore procedure is completed as soon as the server is brought to the online mode.
onmode -m

The SAP system can now be started (as user adm)
startsap r3

Additional key words

Cold Restore, Salvage Logs, salvage logs, ondatartr