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Replication Guide and Reference

Reverting to Version 1 with FALLBACK

You can revert to Version 1 by running the ASNMIG command with the FALLBACK action. You need to fall back from all Version 5 Apply program processes before you fall back from associated Version 5 Capture program processes. You can fall back from Apply program processes in whichever order you choose.

After you fall back to Version 1, you can use the same migration process as described in "Migrating Data with MIGRATE". You cannot fall back to Version 1 after executing the CLEANUP action, because all unused Version 1 control tables and views are dropped.

When fallback occurs at the source server, ASN.IBMSNAP_CRITSEC, ASN.IBMSNAP_UOW, and ASN.IBMSNAP_CCPPARMS remain in their altered format with the additional columns, which do not cause any conflicts with the Version 1 Capture and Apply programs.

If you successfully migrate both Capture and Apply and you subsequently used the Control Center to define new replication sources and subscriptions before falling back, all new Version 5 replication sources and subscriptions are lost. When this happens, the migration program issues an informational message.

Falling Back from an Apply Program Process

To fall back from Version 5 to Version 1 for an Apply program process:

  1. Stop the Version 5 Apply program that you are migrating.

  2. Enter the following command: 
    ASNMIG FALLBACK D=
mig_db T=
rout_serv C=
v5_ctrl_serv U=
sub_id (V=
ver)

    Where:

    mig_db
    Name of the migration database where the global control tables are stored. This is a required parameter.

    rout_serv
    Server where the routing table resides. This is a required parameter.

    v5_ctrl_serv
    Version 5 control server, which contains the control tables for the Apply program process. This is a required parameter.

    sub_id
    Subscriber ID of an Apply program process. This is a required parameter.

    ver
    Version of the migration data that you want to fall back to. If you do not specify this parameter, ASNMIG selects the latest version number. This is an optional parameter.

  3. Examine the fallback report (FALLBACK.RPT) to determine if the program executed successfully.

  4. Make sure the Version 1 Apply program still exists on the source server where it will execute. To install the program, see DataPropagator Relational Guide (SC26-3399-05) for your particular platform.

  5. Bind the Version 1 Apply program as described in DataPropagator Relational Guide (SC26-3399-05) for your particular platform.

  6. Start the Version 1 Apply program as described in DataPropagator Relational Guide (SC26-3399-05) for your particular platform after you successfully execute the FALLBACK action.

When you start ASNMIG FALLBACK for a target server, the program performs the following actions:

  1. Creates userid.IBMSNAP_ROUTING, copies data from userid.IBMSNAP_ROUTING1 to it, then drops userid.IBMSNAP_ROUTING1.

  2. Copies back the information in the Version 5 common subscription tables to the IBMSNAP_REF_CNTL and IBMSNAP_TRAIL tables at the Version 1 control server. It matches the Version 1 DATA_SERVER, BASE_OWNER and table, COPY_SERVER, and COPY_OWNER and table to the Version 5 SOURCE_SERVER, SOURCE_OWNER and table, TARGET_SERVER, and TARGET_OWNER and table, respectively.

If auto-registration is detected at the target server, FALLBACK instructs you to enter the following command to fall back the ASN.IBMSNAP_REGISTER and userid.ASN. timestampPC tables after the fallback of this Apply program process is complete: 

ASNMIG FALLBACK D=
mig_db S=
v5_targ_serv (V=
ver)

Auto-registration occurs when the TARGET_OWNER and TARGET_TABLE columns in the subscriber's ASN.IBMSNAP.SUBS_MEMBR table are the same as the SOURCE_OWNER and SOURCE_TABLE columns in the ASN.IBMSNAP_REGISTER table at the target server.

You can fall back the ASN.IBMSNAP_REGISTER and userid.ASN. timestampPC tables after the fallback of this Apply program process is finished.

Falling Back from a Capture Program Process

To fall back from Version 5 to Version 1 for a Capture program process:

  1. Stop the Capture program.

  2. Enter the following command: 
    ASNMIG FALLBACK D=
mig_db S=
source_serv (V=
ver)

    Where:

    mig_db
    Name of the migration database where the global control tables are stored. This is a required parameter.

    source_serv
    Source server of Version 5. This is a required parameter.

    ver
    Version of the migration data that you want to fall back to. If you do not specify this parameter, ASNMIG selects the latest version number. This is an optional parameter.

  3. Examine the fallback report (FALLBACK.RPT) to determine if the program executed successfully.

  4. Make sure the Version 1 Capture program is installed on the source server. To install the program, see DataPropagator Relational Guide (SC26-3399-05) for your particular platform.

  5. Bind the Version 1 Capture program as described in DataPropagator Relational Guide (SC26-3399-05) for your particular platform.

  6. Warm start the Version 1 Capture program as described in DataPropagator Relational Guide (SC26-3399-05) for your particular platform after you successfully execute the FALLBACK action.

When you start ASNMIG FALLBACK for a source server, the program performs the following actions:

  1. Drops the ASN.IBMSNAP_CD_CNTL view.

  2. Creates the ASN.IBMSNAP_CD_CNTL table, then copies data to it from the Version 1 ASN.IBMSNAP_CD_CNTL1 and Version 5 ASN.IBMSNAP_REGISTER tables.

  3. Drops the ASN.IBMSNAP_CD_CNTL1 table.

  4. Drops the Version 1 userid.ASN. timestampPC views and creates the Version 1 userid.ASN. timestampPC tables.

  5. Copies data from the Version 1 backup pruning control tables and the Version 5 userid.ASN. timestampPC table to the Version 1 pruning control tables.

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