Generating a foreign copy using replication functions

The following replication functions of the storage systems can be used to create foreign copies under SESAM/SQL:

• TimeFinder/Mirror (Symmetrix):
  Complete copy of the data on additional mirror units, also called Business Continuance Volume (BCVs)

• TimeFinder/Clone (Symmetrix):
  Directly available copy of the data, implemented as a complete copy (with /ACTIVATE-CLONE ..., COPY-COMPLETE-DATA=*YES)

  TimeFinder/Mirror and TimeFinder/Clone can also be employed in conjunction with SRDF.

  The product TimeFinder/Snap cannot be used to create foreign copies as it does not create a complete copy of the original.

• SnapView Clone (CLARiiON CX) :
  Directly available copy of the data, implemented as a complete copy (with /ACTIVATE-CLONE ..., COPY-COMPLETE-DATA=*YES)

  The SnapView Snap product cannot be used to create foreign copies as it does not create a complete copy of the original.

• Equivalent Copy (EC, ETERNUS DX):
  Directly available copy of the data, implemented as a complete copy (with /ACTIVATE-CLONE ..., COPY-COMPLETE-DATA=*YES)

  The product Produkt SnapOPC+ cannot be used to create foreign copies as it does not create a complete copy of the original.

Foreign copies from mirror units are created by means of the following general operator actions:

• Synchronizing the original and mirror disks

• Separating the original and mirror disks

• Creating a foreign copy of the mirror disk (separate processing)

• If required, resynchronizing the original and mirror disks

The required commands are described in detail in the “SHC-OSD (BS2000)” manual. There you will also find figures which illustrate how a disk is separated and synchronized.

Procedure for generating foreign copies with replication functions

The diagram illustrates how SESAM/SQL, the replication functions of the disk storage systems, and BS2000 interact when foreign copies are created. For explanations.

Figure 33: Creating a foreign copy using mirror units

1. Use the administration statement BEGIN-LOCK-SEQUENCE to open a lock sequence.

2. Close the database at logical level with the administration statement PREPARE-FOREIGN-COPY. This interrupts the space update by means of a transaction lock. The transaction lock to prevent updates is retained until the end of the lock sequence. The database consists of the CAT-REC file, the catalog space and the user spaces.

3. Use the SHC-OSD command HOLD-MULTI-MIRRORING to separate the multi-mirror pair on the Symmetrix system. The ACTIVATE-CLONE command is used to separate a clone unit in TimeFinder/Clone and SnapView/Clone.

   You use the NEW-PUBSET parameter to modify the CATID of the mirror unit. The mirror unit now corresponds to a copy of the database with a different CATID but the same name.

   • BS2000 requires a modification to the CATID since the Additional Mirror / Clone Unit is to be imported into the same BS2000 system as the original database. The Additional Mirror / Clone Unit can be imported unchanged into another BS2000 system.

   • SESAM/SQL requires unique names, that are independent of the CATID, within the set of CATIDs supervised by the DBH.
     To ensure that names are unique, you must assign the mirror unit a CATID that is not present in the CATID list of the DBH which is used to address the original database.

   If you have not assigned a CATID list to the DBH or if the copy is to be located at a CATID in the CATID list, then you must change the name of the copy in COPY-FILE (step 6).

4. Use the administration statement END-FOREIGN-COPY to remove a “copy pending” status resulting from a utility statement that preceded the foreign copy. You can also change the database status after PREPARE-FOREIGN-COPY with physical closure of the database files.

5. Use the administration statement END-LOCK-SEQUENCE to terminate the lock sequence and remove the transaction lock blocking updates to the original database. The database will be logically opened the next time it is accessed.

6. Use the BS2000 command COPY-FILE to create a copy of the mirror unit. Please remember that SESAM/SQL requires unique names independently of the CATID itself within the CATIDs considered by the DBH.

   • To ensure that names are unique, you must assign the copy a CATID that is not present in the CATID list of the DBH which is used to address the original database.

   • When you use COPY-FILE, you can choose a new name for the copy. The name only needs to be modified during the copy process if you have not assigned a CATID list to the DBH or if the copy is to be located at a CATID in the CATID list.

7. You can use the command RESUME-MULTI-MIRRORING to reconstruct the multimirror pair on the Symmetrix system. A clone session is restarted in TimeFinder/Clone and SnapView/Clone using the RESTART-CLONE-SESSION command.

   After this a new foreign copy of the original database can be generated.

8. Depending on the intended usage, you must perform one of the following operations in order to use the copy of the mirror unit as a foreign copy for SESAM/SQL applications:

   • CREATE REPLICATION
     You assign the DBH a CATID list that contains the CATID of the copy but not that of the original database. You can now create a replication of the original database using the utility statement CREATE REPLICATION.

   • RECOVER ... FOREIGN COPY
     First of all you must copy the files in the foreign copy itself to the corresponding spaces in the original database. You can then repair or reset the original database with the utility statement RECOVER ... FOREIGN COPY.

   • ADD-SQL-DB-CATALOG-ENTRY
     You assign the DBH a CATID list that contains the CATID of the copy but not that of the original database. You enter the foreign copy as a duplicate of the original database in the SQL database catalog of this DBH.

If the copy is created from the mirrorunit using HSMS then you do not need to perform steps 3 - 7 yourself. HSMS runs these provided that you have specified the parameter CONCURRENT-COPY=*YES(WORK-FILE-NAME=*BY-ADD-MIRROR-UNIT) in the BACKUP-FILES statement.

Physically opened files whose consistency has been ensured by means of PREPARE-FOREIGN-COPY can be backed up with HSMS.

SESAM backup copies can also be created from mirror units, see “Creating SESAM backup copies from mirror units using HSMS”.

Sample procedure

In the procedure below an Additional Mirror / Clone Unit is split using SESADM:

/ASSIGN-SYSDTA  TO-FILE=*SYSCMD
/START-SESADM
//START-DBH-ADMINISTRATION ...
//BEGIN-LOCK-SEQUENCE
//PREPARE-FOREIGN-COPY SELECT=*LOGICAL(CATALOG-NAME=...)
//HOLD-PROGRAM
/HOLD-MULTI-MIRRORING ... bzw. /ACTIVATE-CLONE ...
/RESUME-PROGRAM
//END-FOREIGN-COPY SELECT=*LOGICAL(CATALOG-NAME=...)
//END-LOCK-SEQUENCE
//END

The database files on the split mirror unit can now be backed up.