Offline restructuring of DEDB databases
View Patent ↗An IMS DEDB database restructure operation creates an empty offline DEDB having the desired structure. The offline database is populated with data from a source (online) database while keeping the source database online (i.e., available for access and update operations). Updates to the source database made during this process are selectively processed in parallel with the offline DEDB load operation. When the contents of the offline database is substantially the same as the source or online database, the source database is taken offline, final updates to the offline database are applied whereafter the offline database is brought online, thereby replacing the source database. It is significant to note that updates occurring to the source or online DEDB are applied to the offline DEDB.
1. A method for changing a randomizer function in a Data Entry Data Base (DEDB), the method comprising:
registering, using at least one processor, an area of an active DEDB with a change module, the registered area of the active DEDB having a first randomizer function, the first randomizer function being used to determine a location of a database record within the registered area;
allocating, using the at least one processor, an area for an offline shadow DEDB, the area for the offline shadow DEDB having a second randomizer function that differs from the first randomizer function;
populating the area of the offline shadow DEDB with data from the registered area of the active DEDB and, during the populating:
identifying a modification to the active DEDB, and
in response to determining that the modification is directed to the registered area, reflecting the modification in the offline shadow DEDB;
replacing the area of the active DEDB with the area of the shadow DEDB; and
making the area of the shadow DEDB database active.
2. The method of claim 1 , wherein the registered area represents less than the entire active DEDB.
3. The method of claim 1 , wherein the modification is an update to a first database record at a first location in the registered area and reflecting the modification in the offline shadow DEDB includes using the second randomizer function to determine a second location for the first database record in the area of the offline shadow DEDB.
4. The method of claim 3 , wherein reflecting the modification in the offline shadow DEDB further includes:
determining whether the first location occurs in a unit of work already populated in the offline shadow DEDB;
ignoring the update when it is determined that the modification does not occur in a unit of work already populated in the offline shadow DEDB; and
applying the update at the second location in the area of the offline shadow DEDB when the update does occur in a unit of work already populated in the offline shadow DEDB.
5. The method of claim 1 , further comprising:
determining whether a small number of modifications await to be applied to the offline shadow DEDB;
quiescing the registered area of the active DEDB;
applying the small number of modifications to the offline shadow DEDB; and
performing the replacing after applying the small number of modifications.
6. The method of claim 1 , wherein reflecting the modification in the offline shadow DEDB includes:
identifying a key for the modification;
transforming the key using the second randomizer function to determine a location; and
writing a database record from the modification at the location.
7. A non-transitory program storage device comprising instructions for causing a programmable control device to perform the method of claim 1 .
8. A computer system comprising:
a first storage device having stored therein an online data entry database (DEDB) having a first area, the first area having a first randomizer function that is used to determine a location of a particular record within the area;
a database management system (DBMS) communicatively coupled to the first storage device, wherein the DBMS is configured to modify the online DEDB;
at least one processor; and
a memory storing instructions that, when executed by at least one processor, cause the computer system to perform operations comprising:
registering an area of an active DEDB with a change module,
allocating an offline shadow DEDB having a second area, the second area having a second randomizer function that differs from the first randomizer function,
populating the second area with data from the registered area while the second area is offline and, during the populating:
receiving a notification of a modification to the online DEDB from the DBMS, and
in response to determining that the modification is directed to the registered area, reflecting the modification in the second area,
replacing the area of the online DEDB with the second area, and
making the second area active.
9. The computer system of claim 8 , wherein the registered area represents less than the entire active DEDB.
10. The computer system of claim 8 , wherein populating the second area includes:
quiescing a first unit of work (UOW) in the area of the active DEDB;
notifying the change module that the first UOW has been copied to the offline shadow DEDB;
reading the first UOW from the active DEDB;
writing the first UOW into the offline shadow DEDB; and
releasing the first UOW so that it may be updated in the active DEDB.
11. The computer system of claim 8 , wherein the modification is an update to a first database record at a first location in the registered area and reflecting the modification in the second area includes using the second randomizer function to determine a second location for the first database record in the second area.
12. The computer system of claim 11 , wherein reflecting the modification in the second area further includes:
determining whether the first location occurs in a unit of work already populated in the offline shadow DEDB;
ignoring the update when it is determined that the modification does not occur in a unit of work already populated in the offline shadow DEDB; and
applying the update at the second location in the second area when the update does occur in a unit of work already populated in the offline shadow DEDB.
13. The computer system of claim 8 , wherein the instructions further include instructions that, when executed by the at least one processor, cause the computer system to perform operations comprising:
determining whether a small number of modifications await to be applied to the second area;
quiescing the registered area of the active DEDB;
applying the small number of modifications to the second area; and
performing the replacing after applying the small number of modifications.
14. The computer system of claim 8 , wherein reflecting the modification in the second area includes:
identifying a key for the modification;
transforming the key using the second randomizer function to determine a location in the second area; and
writing a database record from the modification at the location in the second area.
15. The computer system of claim 8 , wherein the computer system includes an IMSPlex, where the DBMS is associated with a first computing device of the computer system and the computer system further includes a second DBMS communicatively coupled to the active DEDB and associated with a second computing device and the second DBMS sends the notification of the modification to the active DEDB.
16. A method comprising:
registering, using at least one processor, a first area of an active DEDB with a change module, the first area of the active DEDB defined as comprised of a first quantity of units of work (UOWs);
allocating, using the at least one processor, a shadow DEDB having a second area, the second area defined as comprised of a second quantity of UOWs, the second quantity differing from the first quantity;
populating the second area with data from the first area and, during the populating:
identifying a modification to the active DEDB, and
in response to determining that the modification is directed to the first area, reflecting the modification in the second area;
replacing the first area with the second area; and
making the second area of the shadow DEDB active.
17. The method of claim 16 , wherein the registered area represents less than the entire active DEDB.
18. The method of claim 16 , wherein reflecting the modification in the second area includes:
identifying a key for the modification;
transforming the key using a randomizer function to determine a location in the second area; and
writing a database record from the modification at the location in the second area.
19. The method of claim 18 , wherein writing the database record occurs while the second area is offline.
20. The method of claim 18 , wherein reflecting the modification in the second area further includes:
determining whether the location is in a unit of work already populated in the second area;
ignoring the modification when it is determined that the modification does not occur in a unit of work already populated in the second area; and
applying the modification at the second location in the second area when the update does occur in a unit of work already populated in the second area.