Allocating database data sets
You can specify dynamic allocation either explicitly or implicitly. If you use implicit dynamic allocation, you may be able to eliminate changes to JCL and job documentation when data set groups or area data sets are added or deleted.
Always store dynamic allocation members in a library pointed to by an IMSDALIB, MDALIB, DFSRESLB, or STEPLIB DD statement. These dynamic allocation members are created by assembling and link-editing the Dynamic Allocation macro (DFSMDA). See the IMS documentation from IBM for information about the Dynamic Allocation macro. For high-availability large databases (HALDBs) databases, dynamic allocation information is stored in the RECON.
When you are recovering a preallocated multi-volume OSAM database data set and are not using the IDCAMS keyword, it is important that the VTOC entries reflect the correct volume serial sequence numbers. If you use multiple DD statements to preallocate space for each volume, the volume sequence fields will be incorrect.
For DEDBs that are registered, the area data set name stored in DBRC is used for dynamic allocation. If the DEDB is not registered, dynamic allocation members are retrieved from a library in the same manner as DL/I.
The Recovery utility allocates the database data sets after DBRC authorization is complete. When the recovery is complete, the Recovery utility dynamically deallocates the database and area data sets.
The following table describes the effect of the DBALLOC keyword in the recovery process of full-function databases when used with the DBRC and DDN keywords.
DBALLOC used with DL/I databases
DBALLOC | DBRC | DDN | Result |
|---|---|---|---|
N | Y or N | Omitted (implied) | Recover all database data sets for the named DBD whose DD names are specified in the JCL |
ddname (explicit) | Recover the database data set for the named DBD whose DD name is specified with the DDN keyword and is specified in the JCL | ||
Y | Y or N | Omitted (implied) | Recover all database data sets for the named DBD whose DD names match the dynamic allocation member stored in IMSDALIB, MDALIB, DFSRESLB, or STEPLIB |
ddname (explicit) | Recover the database data set for the named DBD whose DD name is specified with the DDN keyword and matches the dynamic allocation member stored in IMSDALIB, MDALIB, DFSRESLB, or STEPLIB |
The following table describes the effect of the DBALLOC keyword when used with the DBRC and ADDN keywords in the recovery process of DEDB databases.
DBALLOC used with DEDB databases
DBALLOC | DBRC | ADDN | Result |
|---|---|---|---|
N | N | Omitted | Recover the area data sets whose DD name matches the database area name and is specified in the JCL |
ddname1,ddname2,.... | Recover one or more area data sets whose DD names are specified with the ADDN keyword and are specified in the JCL | ||
* | Ignored | ||
Y | N | Omitted | Recover the area data sets whose DD name matches the database area name and matches the dynamic allocation member stored in IMSDALIB, MDALIB, DFSRESLB, or STEPLIB |
ddname1,ddname2,.... | Recover the area data sets whose DD names are specified with the ADDN keyword and match the dynamic allocation members stored in IMSDALIB, MDALIB, DFSRESLB, or STEPLIB | ||
* | Ignored | ||
N | Y | Omitted | Recover the first area data set whose DD name is defined in DBRC and is specified in the JC. |
ddname1,ddname2,.... | Recover one or more area data sets whose DD names are specified with the ADDN keyword and are specified in the JCL. DBRC validates each area data set | ||
* | Recover all area data sets whose DD names are defined in DBRC and specified in the JCL | ||
Y | Y | Omitted | Recover the first area data set whose DD name and data set name are defined in DBRC |
ddname1,ddname2,... | Recover one or more area data sets whose DD names are specified with the ADDN keyword and match the area data set names defined in DBRC. DBRC validates each area data set | ||
* | Recover all area data sets whose DD names are defined in DBRC and match the area data set names defined in DBRC |
This section contains the following topics: