Transfer track format information for tracks in cache at a first processor node to a second process node to which the first processor node is failing over

• US 10,540,246 B2
• Filed: 07/27/2017
• Issued: 01/21/2020
• Est. Priority Date: 07/27/2017
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Anderson, Kyler A., Ash, Kevin J., Borlick, Matthew G., Gupta, Lokesh M.
• Primary Examiner(s): Duncan, Marc
• Application Number:
  US15/662,186
• Publication Number:
  US 20190034303A1
• Time in Patent Office: 908 Days
• CPC Class Codes: G06F 11/2092 Techniques of failing over between control units
• CPC Class Codes: G06F 12/0842 for multiprocessing or multitasking
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 2201/805 Real-time
• CPC Class Codes: G06F 2212/601 Reconfiguration of cache memory

Abstract

Provided are a computer program product, system, and method for managing failover from a first processor node including a first cache to a second processor node including a second cache. Storage areas assigned to the first processor node are reassigned to the second processor node. For each track indicated in a cache list of tracks in the first cache for the reassigned storage areas, the first processor node adds a track identifier of the track and track format information indicating a layout and format of data in the track to a cache transfer list. The first processor node transfers the cache transfer list to the second processor node. The second processor node uses the track format information transferred with the cache transfer list to process read and write requests to tracks in the reassigned storage areas staged into the second cache.

Claims

1. A computer program product for managing failover from a first processor node including a first cache to a second processor node including a second cache, wherein the first cache and second cache are used to cache tracks from a storage, the computer program product comprising a computer readable storage medium having computer readable program code executed in the first and second processor nodes to cause the first and second processor nodes to perform operations, the operations comprising:

reassigning storage areas assigned to the first processor node to the second processor node;

for each track indicated in a cache list of tracks in the first cache for the reassigned storage areas, determining whether track format information is available for the track in the first cache and adding, by the first processor node, a track identifier of the track and track format information indicating a layout and format of data in the track to a cache transfer list in response to determining that track format information is available for the track in the first cache;

transferring, by the first processor node, the cache transfer list to the second processor node; and

using, by the second processor node, the track format information transferred with the cache transfer list to process read and write requests to tracks in the reassigned storage areas staged into the second cache.

2. The computer program product of claim 1, wherein the operations further comprise:

performing a code load on the first processor node after transferring the cache transfer list to the second processor node; and

in response to completing the code load, reassign the reassigned storage areas from the second processor node back to the first processor node.

3. The computer program product of claim 1, wherein the cache list comprises a first cache list, wherein the cache transfer list comprises a first cache transfer list, wherein the storage areas comprise first storage areas, wherein second storage areas in the storage are assigned to the second processor node, wherein the operations further comprise:

reassigning the first storage areas, previously reassigned to the second processor node, back to the first processor node;

for each track for the first storage areas in the second cache indicted in a second cache list of tracks in the second cache, adding, by the second processor node, information on a track identifier of the track and track format information indicating a layout of data in the track, indicated in track metadata for the track in the storage, to a second cache transfer list;

transferring, by the second processor node, the second cache transfer list to the first processor node; and

using, by the first processor node, the track format information transferred with the second cache transfer list to process a track in the first storage areas staged into the first cache after receiving the second cache transfer list.

4. The computer program product of claim 1, wherein the track format information comprises a track format code defined in a first track format table at the first processor node and a second track format table at the second processor node associating track format codes with track format metadata.

5. The computer program product of claim 1, wherein the operations further comprise:

maintaining, by the second processor node, a demoted track list indicating tracks demoted from the second cache for which track format information is maintained before reassigning the storage areas; and

including track identifiers in the cache transfer list into the demoted track list.

6. The computer program product of claim 5, wherein the operations further comprise:

merging subsets of entries from the demoted track list and the cache transfer list into the demoted track list.

7. The computer program product of claim 5, wherein the operations further comprise:

temporary allocating, at the second processor node, additional memory space for the demoted track list to include the track identifiers in the transfer cache list while the reassigned storage areas are assigned to the second processor node.

8. The computer program product of claim 1, wherein the track format information comprises a track format code defined in a first track format table at the first processor node and a second track format table at the second processor node associating track format codes with track format metadata, wherein the second processor node uses the cache transfer list to determine track format information for a track by performing:

staging, by the second processor node, a track for the reassigned storage areas into the second cache;

generating a cache control block for the staged track;

determining whether there is track format information for the staged track that was transferred with the cache transfer list to the second processor node; and

including the track format information for the staged track in the cache control block for the staged track in response to determining that there is the track format information for the staged track from the cache transfer list.

9. The computer program product of claim 1, wherein the operations performed by the second processor node in response to receiving the cache transfer list further comprise:

for at least one track indicated in the cache transfer list, generating a demoted track cache control block indicating the track and the track format information for the track in the cache transfer list, and

wherein the using the track format information transferred with the cache transfer list comprises;

generating a cache control block for a track staged into the second cache;

determining whether there is a demoted cache control block for the track staged into the second cache; and

including the track format information in the demoted cache control block for the track staged into the second cache in the cache control block for the track staged into the second cache.

10. The computer program product of claim 1, wherein the operations performed by the second processor node in response to receiving the cache transfer list further comprise for each track indicated in the cache transfer list:

generating a demoted cache control block indicating the track and the track format information for the track in the cache transfer list;

determining an entry in a demoted cache control block directory, having a plurality of entries, based on a track identifier in the demoted cache control block; and

indicating the demoted cache control block in the determined entry in the demoted cache control block directory.

11. A system coupled to a storage, comprising:

a first processor node including a first cache to cache tracks from the storage;

a second processor node including a second cache to cache tracks from the storage;

wherein the first processor node and second processor node perform a failover from the first processor node to the second processor node by performing operations, the operations comprising;

reassigning storage areas assigned to the first processor node to the second processor node;

for each track indicated in a cache list of tracks in the first cache for the reassigned storage areas, determining whether track format information is available for the track in the first cache and adding, by the first processor node, a track identifier of the track and track format information indicating a layout and format of data in the track to a cache transfer list in response to determining that track format information is available for the track in the first cache;

transferring, by the first processor node, the cache transfer list to the second processor node; and

using, by the second processor node, the track format information transferred with the cache transfer list to process read and write requests to tracks in the reassigned storage areas staged into the second cache.

12. The system of claim 11, wherein the cache list comprises a first cache list, wherein the cache transfer list comprises a first cache transfer list, wherein the storage areas comprise first storage areas, wherein second storage areas in the storage are assigned to the second processor node, wherein the operations further comprise:

reassigning the first storage areas, previously reassigned to the second processor node, back to the first processor node;

for each track for the first storage areas in the second cache indicted in a second cache list of tracks in the second cache, adding, by the second processor node, information on a track identifier of the track and track format information indicating a layout of data in the track, indicated in track metadata for the track in the storage, to a second cache transfer list;

transferring, by the second processor node, the second cache transfer list to the first processor node; and

using, by the first processor node, the track format information transferred with the second cache transfer list to process a track in the first storage areas staged into the first cache after receiving the second cache transfer list.

13. The system of claim 11, wherein the operations further comprise:

maintaining, by the second processor node, a demoted track list indicating tracks demoted from the second cache for which track format information is maintained before reassigning the storage areas; and

including track identifiers in the cache transfer list into the demoted track list.

14. The system of claim 11, wherein the track format information comprises a track format code defined in a first track format table at the first processor node and a second track format table at the second processor node associating track format codes with track format metadata, wherein the second processor node uses the cache transfer list to determine track format information for a track by performing:

staging, by the second processor node, a track for the reassigned storage areas into the second cache;

generating a cache control block for the staged track;

determining whether there is track format information for the staged track that was transferred with the cache transfer list to the second processor node; and

including the track format information for the staged track in the cache control block for the staged track in response to determining that there is the track format information for the staged track from the cache transfer list.

15. The system of claim 11, wherein the operations performed by the second processor node in response to receiving the cache transfer list further comprise:

for at least one track indicated in the cache transfer list, generating a demoted track cache control block indicating the track and the track format information for the track in the cache transfer list, and

wherein the using the track format information transferred with the cache transfer list comprises;

generating a cache control block for a track staged into the second cache;

determining whether there is a demoted cache control block for the track staged into the second cache; and

including the track format information in the demoted cache control block for the track staged into the second cache in the cache control block for the track staged into the second cache.

16. The system of claim 11, wherein the operations performed by the second processor node in response to receiving the cache transfer list further comprise for each track indicated in the cache transfer list:

generating a demoted cache control block indicating the track and the track format information for the track in the cache transfer list;

determining an entry in a demoted cache control block directory, having a plurality of entries, based on a track identifier in the demoted cache control block; and

indicating the demoted cache control block in the determined entry in the demoted cache control block directory.

17. A method for managing failover from a first processor node including a first cache to a second processor node including a second cache, wherein the first cache and second cache are used to cache tracks from a storage, comprising:

reassigning storage areas assigned to the first processor node to the second processor node;

for each track indicated in a cache list of tracks in the first cache for the reassigned storage areas, determining whether track format information is available for the track in the first cache and adding, by the first processor node, a track identifier of the track and track format information indicating a layout and format of data in the track to a cache transfer list in response to determining that track format information is available for the track in the first cache;

transferring, by the first processor node, the cache transfer list to the second processor node; and

using, by the second processor node, the track format information transferred with the cache transfer list to process read and write requests to tracks in the reassigned storage areas staged into the second cache.

18. The method of claim 17, wherein the cache list comprises a first cache list, wherein the cache transfer list comprises a first cache transfer list, wherein the storage areas comprise first storage areas, wherein second storage areas in the storage are assigned to the second processor node, further comprising:

reassigning the first storage areas, previously reassigned to the second processor node, back to the first processor node;

for each track for the first storage areas in the second cache indicted in a second cache list of tracks in the second cache, adding, by the second processor node, information on a track identifier of the track and track format information indicating a layout of data in the track, indicated in track metadata for the track in the storage, to a second cache transfer list;

transferring, by the second processor node, the second cache transfer list to the first processor node; and

using, by the first processor node, the track format information transferred with the second cache transfer list to process a track in the first storage areas staged into the first cache after receiving the second cache transfer list.

19. The method of claim 17, further comprising:

maintaining, by the second processor node, a demoted track list indicating tracks demoted from the second cache for which track format information is maintained before reassigning the storage areas; and

including track identifiers in the cache transfer list into the demoted track list.

20. The method of claim 17, wherein the track format information comprises a track format code defined in a first track format table at the first processor node and a second track format table at the second processor node associating track format codes with track format metadata, wherein the second processor node uses the cache transfer list to determine track format information for a track by performing:

staging, by the second processor node, a track for the reassigned storage areas into the second cache;

generating a cache control block for the staged track;

determining whether there is track format information for the staged track that was transferred with the cache transfer list to the second processor node; and

including the track format information for the staged track in the cache control block for the staged track in response to determining that there is the track format information for the staged track from the cache transfer list.

21. The method of claim 17, wherein in response to receiving the cache transfer list, the second processing node further performs:

for at least one track indicated in the cache transfer list, generating a demoted track cache control block indicating the track and the track format information for the track in the cache transfer list, and

wherein the using the track format information transferred with the cache transfer list comprises;

generating a cache control block for a track staged into the second cache;

determining whether there is a demoted cache control block for the track staged into the second cache; and

including the track format information in the demoted cache control block for the track staged into the second cache in the cache control block for the track staged into the second cache.

22. The method of claim 17, wherein in response to receiving the cache transfer list, the second processor node further performs for each track indicated in the cache transfer list:

generating a demoted cache control block indicating the track and the track format information for the track in the cache transfer list;

determining an entry in a demoted cache control block directory, having a plurality of entries, based on a track identifier in the demoted cache control block; and

indicating the demoted cache control block in the determined entry in the demoted cache control block directory.