IBM Tivoli Storage Manager, Version 7.1

A simultaneous-write error during a client store operation

In this example, data is not written to one copy storage pool in a simultaneous-write operation.

You specify COPYPOOL1 and COPYPOOL2 as copy storage pools for DISKPOOL and you set the value of the COPYCONTINUE parameter to YES. You also specify ACTIVEDATAPOOL as the active-data pool for DISKPOOL. This configuration is identical to the configuration in the first example.

When files A, B, C, D, and E are backed up, the following events occur:

An error occurs while writing to COPYPOOL1, and it is removed from the copy storage pool list that is held in memory by the server. The transaction fails.
Because the value of the COPYCONTINUE parameter is YES, the client tries the backup operation again. The in-memory copy storage pool list, which is retained by the server for the duration of the client session, no longer contains COPYPOOL1.
Files A and B are simultaneously written to DISKPOOL, ACTIVEDATAPOOL, and COPYPOOL2.
Files C and D are simultaneously written to DISKPOOL and COPYPOOL2.
File E is simultaneously written to TAPEPOOL and COPYPOOL2.

See Figure 1.

Figure 1. Inheriting a list of copy storage pools

One client belonging to the normal domain sends three files to the server. The other client belonging to the fastrestore domain sends two files to the server. Four of the files are copied to the disk storage pool. One file is copied to the next storage pool. Copies of the five files are sent to one of the copy storage pools. The other copy storage pool, which was removed for the duration of the client session, does not receive any copies. The active-data pool receives the two files belonging to the client in the fastrestore domain.

In this scenario, if the primary storage pools and COPYPOOL2 become damaged or lost, you might not be able to recover your data. For this reason, issue the following BACKUP STGPOOL command for the copy storage pool that failed:

backup stgpool diskpool copystgpool1
backup stgpool tapepool copystgpool1

Suppose, in this scenario, that an error occurred while writing to ACTIVEDATAPOOL, rather than COPYPOOL1. In this situation, ACTIVEDATAPOOL is removed from the active-data pool list held in memory by the server, and the transaction fails. The client tries the backup operation again. The in-memory active-data pool list does not contain ACTIVEDATAPOOL. Files A, B, C, and D are written simultaneously to DISKPOOL, COPYPOOL1, and COPYPOOL2. File E is written to TAPEPOOL, COPYPOOL1, and COPYPOOL2. However, files A and B are not written to the active-data pool.

You can still recover the primary storage pools from COPYPOOL1 and, if necessary, COPYPOOL2. However, if you want active backup data available in the active-data pool for fast client restores, you must issue the following command:

copy activedata diskpool activedatapool

As a precaution, issue the BACKUP STGPOOL and COPY ACTIVEDATA commands after the backup operation has completed. Data that is simultaneously written to copy storage pools or active-data pools during migration is not copied when primary storage pools are backed up or when active data is copied.

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