The DB2 Data Links Manager for AIX Quick Beginnings book and the DB2 Data Links Manager for Windows NT Quick Beginnings book are not available in HTML format.
Windows NT 4.0 FixPak 4 is a prerequisite for Data Links on Windows NT.
If you are registering a Windows NT instance on an AIX Data Links Manager, the instance name must be in uppercase.
An SQL SELECT on a DATALINK column which was defined with the "READ PERMISSION DATABASE" option will return the URL or file name with an access token embedded within the name. This access token has an expiration time, as defined by the DL_EXPINT database configuration parameter. When using an NFS client to access such files, you may find that the access token does not expire appropriately. This can be due to caching done by the NFS client. It has been observed that the use of long file names (greater than 12 characters) may mitigate this problem.
Whenever you remotely mount a DLFS file system via NFS, you may also want to include the mount option "noac". For example:
mount -o noac birdcage:/dlink /dlink
The Version 5.2 manual documents a specific set of environment variables that must be set for the Data Links Manager to function properly. These are:
DLFM_INSTALL_PATH DLFM_PORT DLFM_LOG_LEVEL DB2_RR_TO_RS DLFM_BACKUP_DIR_NAME
Version 5.2 to Version 6 migration converts these environment variables to DB2 registry variables. Registry variables offer more function and flexibility than environment variables. However, because of this, it is possible that migration will not be performed exactly as expected. The registry variables should be checked (using the db2set command) after migration.
The following system setup and backup procedures are recommended for easier recovery:
o Place the DLFM database (DLFM_DB), any file systems under control of the
DB2 Data Links Filesystem Filter (DLFF), the DLFM backup directory, and
the DLFM home directory on different file systems. Ensure they do not
share disks.
o Back up any file systems under the control of the DLFF and the DLFM on a storage
manager, such as IBM's ADSM. In the event of disk failure, this will provide
added protection.
o Have one database associated with one or more DB2 Data Links Managers. Avoid having
two databases associated with one DB2 Data Links Manager; otherwise, certain
recovery scenarios will become more complex than is necessary.
o Perform full database backups of the DB2 databases (as well as the DLFM_DB
database on the DB2 Data Links Manager) at regular intervals.
This section lists some of the possible DB2 Data Links Manager failure scenarios and the steps required to recover from them. For a description of recommended procedures for easier recovery, see 14.6 , DB2 Data Links Manager System Setup and Backup Recommendations.
DEFINITIONS
DLFS file system - Registered prefix (example: /dlink)
DLFM backup directory - Directory where files are backed up (example: /home/dlfm/dlfm_backup)
DLFM home directory - Home directory of DLFM user ID (example: /home/dlfm)
DLFM DB2 database - DB2 database that contains all meta-data (DLFM_DB)
DB2 database - Registered database that contains DATALINK data type (example: CROWN)
COMPONENTS THAT MAY REQUIRE RECOVERY
o The DB2 database containing a table which has a DATALINK column
o The DB2 Data Links Manager's database (DLFM_DB)
o Data Links Filesystem Filter (DLFF)
o File systems under the control of the DB2 DLFF which are registered to
the Data Links Manager
o The DB2 Data Links Manager's backup directory
RECOVERY SCENARIOS
The following recovery scenarios may require operations to be performed on both the DB2 node
and the DB2 File Manager node.
The DB2 database will be referred to as "CROWN" throughout all examples, and the DB2 table
containing the DATALINK column will be referred to as "DATALINKTABLE".
Scenario #1A:
DB2 Database is lost or was accidentally dropped, but DB2 backup and log files
are available.
Note: In this scenario, the DB2 database has not been dropped from the DLFM
server.
Recovery Steps:
Step 1. On the DB2 server, enter the following commands:
db2 "restore database CROWN"
db2 "rollforward database CROWN to end of logs"
db2 "reconcile table DATALINKTABLE"
Scenario #1B:
DB2 database explicitly dropped, but DB2 backup and log files are available.
Recovery Steps:
Step 1. Ensure that the drop database operation is complete, and that all files
associated with that database have been unlinked.
Step 2. On the Data Links server enter the following commands:
db2 "connect to dlfm_db"
db2 "select dbid, dbname, dbinst, hostname from dfm_dbid"
db2 "update dfm_dbid set action=5 where dbid=x'35B3D7BE0006BF7B'"
(Set dbid equal to value found in previous step.)
Step 3. On the DB2 server enter the following commands:
db2 "restore database CROWN"
db2 "rollforward database CROWN to end of logs"
db2 "reconcile table DATALINKTABLE"
Scenario #2:
The DLFM_DB database is lost, but the backup and all log files for the DLFM_DB
database are available.
Recovery Steps:
Step 1. On the Data Links server enter the following commands:
db2 "restore database dlfm_db"
db2 "rollforward database dlfm_db to end of logs"
Step 2. On the DB2 server enter the following command:
db2 "connect to CROWN"
db2 "reconcile table DATALINKTABLE"
Scenario #3:
The DLFM_DB database is lost, a backup of the DFLM_DB database is available, but
the not all of the log files are available.
Recovery Steps:
Step 1. On the Data Links server enter the following commands:
db2 "restore database dlfm_db"
db2 "rollforward database dlfm_db to end of logs"
db2 "connect to CROWN"
Step 2. On the DB2 server enter the following command:
db2 "connect to CROWN"
db2 "reconcile table DATALINKTABLE"
Scenario #4:
The DLFS file system is lost.
Recovery Steps:
Step 1. Restore the DLFS file system from your storage manager.
Step 2. On the DB2 Server enter the following command:
db2_recon_aid CROWN
Scenario #5:
The DLFM backup directory is lost.
Recovery Steps:
Restore the DLFM backup directory from your storage manager.
Scenario #6:
The DLFS file system and the DLFM backup directory are lost.
Recovery Steps:
Step 1. Restore the DLFM backup directory from your storage manager.
Step 2. Restore the DLFS file system from your storage manager.
Step 3. On the DB2 Server enter the following command:
db2_recon_aid CROWN
Scenario #7:
The DLFM_DB database, the DLFM backup directory, and the DLFS file system
are lost, but the backup, and all log files for the DLFM_DB database are
available.
Recovery Steps:
Step 1. On the Data Links server enter the following commands:
db2 "restore database dlfm_db"
db2 "rollforward database dlfm_db to end of logs"
Step 2. Restore the DLFM backup directory from your storage manager.
Step 3. Restore the DLFS file system from your storage manager.
Step 4. On the DB2 Server enter the following command:
db2_recon_aid CROWN
Scenario #8:
The DLFM_DB, the DLFS file system, and the DLFM backup directory are lost.
The backup of the DLFM_DB database is available, but not all log
files are available.
Recovery Steps:
Step 1. On the Data Links server enter the following commands:
db2 "restore database dlfm_db"
db2 "rollforward database dlfm_db to end of logs"
Step 2. Restore the DLFM backup directory from your storage manager.
Step 3. Restore the DLFS file system from your storage manager.
Step 4. On the DB2 Server enter the following command:
db2_recon_aid CROWN
Scenario #9:
The DB2 database, the DLFM_DB database, the DLFS file system and DLFM
backup directory are lost, but backup, and all log files for the DLFM_DB
database are available.
Recovery Steps:
Step 1. On the Data Links server enter the following commands:
db2 "restore database dlfm_db"
db2 "rollforward database dlfm_db to end of logs"
Step 2. Restore the DLFM backup directory from your storage manager.
Step 3. Restore the DLFS file system from your storage manager.
Step 4. On the DB2 server enter the following commands:
db2 "restore database CROWN"
db2 "rollforward database CROWN to end of logs"
db2 "connect to CROWN"
db2 "reconcile table DATALINKTABLE"
NOTE: Rollforward to a point-in-time (PIT) may not put tables that have all
DATALINK columns defined as "recovery = no" into
DataLink_Reconcile_Pending (DRP) state. For all such tables, run the
reconcile utility.
In the recovery scenarios, when a DB2 database is dropped or lost, the recovery steps on DB2 should be:
1. Restore the database.
2. Rollforward to end of logs. This will put all tables with
DATALINK columns into DRNP state; they must be reconciled.
3. For each table in DRNP state:
db2 set constraints for <table> to datalink reconcile pending
db2 set constraints for <table> to datalink reconcile pending
immediate unchecked
db2 reconcile <table>
If you change the setting of the DLFM_BACKUP_DIR_NAME registry variable between ADSM and disk at run time, you should be aware that the archived files are not moved to the newly specified archive location. For example, if you start the Data Links File Manager with the DLMF_BACKUP_DIR_NAME registry value set to ADSM, and change the setting of the DLFM_BACKUP_DIR_NAME registry value to a disk location, all newly archived files will be stored in the new location on the disk. The files that were previously archived to ADSM will not be moved to the new disk location.
In the "DB2 Data Links Manager for Windows NT Quick Beginnings" book, the following should be noted in Chapter 5 "Recovering from a Crash on the Data Links Server", in the section "Running RECONCILE after restoring a file system":
The db2_recon_aid utility is not shipped with this release of DB2 Data Links Manager for Windows NT.