# Patent

## Title
Avoiding failure of an initial program load in a logical partition of a data storage system

## Abstract

An initial program load (IPL) of a logical partition (LPAR) is managed by establishing a logical path to the LPAR from a storage controller. When a notice is received by the storage controller from the LPAR that the IPL has commenced, the LPAR address is stored in a data structure. After the storage controller initiates a pack change state interrupt, the stored address is compared with the addresses in a list of all LPARS to which the interrupt is directed. If the list of addresses includes the stored address, the stored address is removed from the list. Thus, the pack change state interrupt is transmitted only to the addresses in the list, leaving the LPAR to complete the IPL without interruption. After the storage controller receives a notice from the LPAR that the IPL has completed, the address of the LPAR is removed from the data structure.

## Background
TECHNICAL FIELD
The present invention relates generally to data storage systems and, in particular, to initial program load operations in a logical partition of a data storage system.
BACKGROUND ART
A data storage system typically includes one or more storage controllers coupled one or more data storage devices, such as hard disk drives (HDDs). The controller receives read and write requests from one or more hosts, processes the requests and, in response reads the requested data from or writes (records) data to the storage device. Larger storage systems enable one physical host to be divided into one or more logical partitions (LPARs) which operate as separate, virtual computers. The LPARs may also run under different operating systems and may execute different application programs. During the initial program load (IPL) of the LPAR, logical paths are established between the host and the storage controller, enabling the two to communicate with each other. Worldwide network node numbers (WWNN) are used to enable links between the communicating devices.
During the IPL of one LPAR, another LPAR may decide to change the state of peer-to-peer remote copy (PPRC) devices, such as from ‘PPRC Full Duplex’ to ‘PPRC Suspended,’ using a ‘Freeze’ command from the host to the storage controller.
When the ‘Freeze’ command is executed, the storage controller sends a pack change or state change interrupt for all devices in a PPRC relationship and to all known paths and path groups. The interrupt may be received by an LPAR which is undergoing an IPL. Should this occur, the LPAR is forced to disrupt the IPL and contend with the pack change interrupt and the ensuing validation and query commands. Because the pack change interrupt is sent one per path for each device that changed state from ‘PPRC Full Duplex’ to ‘PPRC Suspended,’ the large number of pack changes and required command processing can cause the IPL of the LPAR to take a very long time to complete. In some cases, the IPL may fail.
SUMMARY OF THE INVENTION
The present invention reduces the performance impact on an LPAR IPL and reduces the risk of IPL failure due to contending with pack change or state change interrupts received during an IPL. An initial program load (IPL) of a logical partition (LPAR) is managed by establishing a logical path to the LPAR from a storage controller. When a notice is received by the storage controller from the LPAR that the IPL has commenced, the address of the LPAR is stored in a data structure. Subsequently, after the storage controller initiates a pack change state interrupt, the stored address is compared with the addresses in a list of all LPARs to which the pack change state interrupt is directed. If the list of addresses includes the stored address, the stored address is removed from the list. Thus, the pack change state interrupt is transmitted only to the addresses in the list, leaving the LPAR to complete the IPL without interruption. After the storage controller receives a notice from the LPAR that the IPL has completed, the address of the LPAR is removed from the data structure.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a data processing system in which the present invention may be implemented;
FIG. 2 is a flowchart of one aspect of a method of the present invention; and
FIGS. 3, 4, 5 are a flowcharts of further aspects of a method of the present invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a block diagram of a data processing system 100 in which the present invention may be implemented. The system 100 includes one or more hosts, collectively represented by a host 110, one or more storage controllers, collectively represented by a storage controller 120, and one or more storage devices, collectively represented by the storage device 140. The storage device 140 may be any type of storage device, such as hard disk drives, or a combination of devices. The host 110 includes a memory 112 for storing computer-readable code containing program instructions and a processor 114 which executes the instructions stored in the memory 112. The host 110 can create multiple logical partitions (LPARs), two of which are illustrated in FIG. 1 as 116a and 116b. Each LPAR 116a, 116b is capable of running one or more applications 118a, 118b, respectively.
The storage controller 120 includes a memory 122 for storing computer-readable code containing program instructions and a processor 124 which executes the instructions stored in the memory 122. The storage controller also includes host adapters or interfaces, represented by a host adapter 126, through which communications with the host 110 pass, and device adapters or interfaces, represented by a device adapter 128, through which communications with the storage device 140 pass. The storage controller 120 further includes two data structures 130, 132. Either or both of the data structures 130, 132 may be stored in the memory 122 or may be stored in other memory.
A method of the present invention will now be described with reference to the flowcharts of FIGS. 2-5. The method may be executed by the processors 114, 124 from program instructions stored in the memory devices 112, 122, may performed by hardware, such as ASICs in the host 110 and storage controller 120, or by any combination. An LPAR 116a begins an initial program load (step 200) and establishes a communications path with the storage controller 120 (step 202). The LPAR 116a then transmits a command to the storage controller 120 (step 204) notifying the storage controller 120 that an IPL is underway. The command may be a single command having two states, such as an IPL indicator with “set” and “reset” states. Alternatively, the command may be one of two separate commands, the second having an “IPL Complete” indicator as described below. The command, whether a single command or one of two commands, can be part of new orders of the existing defined system operation (DSO) command or new z/Os command(s) that are allowed through most exception conditions, such as “Reserve”, “Long Busy,” etc.
Turning now to FIG. 3 (step 206), the storage controller 120 receives the command from the LPAR 116a (step 300) and stores the address or other identity of the LPAR 116a in a data structure 130 (step 302). Preferably, the data structure 130 is sufficiently large to store the addresses of more than one LPAR which are undergoing an IPL. Also preferably, the address of the LPAR comprises the worldwide network node number (WWNN) of the LPAR 116a. By contrast, a worldwide port number (WWPN) only identifies a host adapter port which is not sufficiently specific of the present invention. The data structure 130 may be a register, a location in the memory 122, a lookup table or any other structure associated with the storage controller 120 capable of storing the identity of the LPAR 116a. 
When the storage controller 120 initiates a pack change state interrupt (FIG. 4, step 404), it generates a list of the addresses, such as the WWNNs, of all devices in a PPRC relationship and to all known paths and path groups (step 406). The list may be stored in a second data structure 132. As with the first data structure 130, the second data structure 132 may be a register, a location in the memory 122, a lookup table or any other structure associated with the storage controller 120 capable of storing the addresses of recipients of the pack change state interrupt. Instead of then queuing the addresses, the storage controller 120 first compares any address(s) in the first data structure identifying LPARs which are undergoing an IPL (step 408). If the address of the LPAR 116a is found in the data structure list 132, the address is removed from the list (step 410). Next, or if the address of the LPAR 116a is not found in the list 132, the storage controller 120 queues the addresses remaining in the 132 list and sends the pack change state interrupt to only those addresses (step 412). Thus, the LPAR 116a and any other LPAR undergoing an IPL will not have to contend with such an interrupt.
When the IPL of the LPAR 116a is completed (step 208, FIG. 2), the LPAR 116a sends a command to the storage controller (step 210) indicating that the IPL is complete. Moving to FIG. 5 (step 212), the storage controller 120 receives the command (step 514). As described above, the command be the second state of the original command or may be a separate command. When the storage controller 120 has received the second command from the LPAR 116a, it removes the address of the LPAR 116a from the first data structure 130 (step 516), allowing the LPAR 116a to receive subsequent pack change state interrupts.
It is important to note that while the present invention has been described in the context of a fully functioning data processing system, those of ordinary skill in the art will appreciate that the processes of the present invention are capable of being distributed in the form of a computer readable medium of instructions and a variety of forms and that the present invention applies regardless of the particular type of signal bearing media actually used to carry out the distribution. Examples of computer readable media include recordable-type media such as a floppy disk, a hard disk drive, a RAM, and CD-ROMs and transmission-type media such as digital and analog communication links.
The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. Moreover, although described above with respect to methods and systems, the need in the art may also be met with a computer program product containing instructions for managing an initial program load (IPL) of a logical partition (LPAR) established in a host or a method for deploying computing infrastructure comprising integrating computer readable code into a computing system for managing an initial program load (IPL) of a logical partition (LPAR) established in a host.

## Claims

1. A method for managing an initial program load (IPL) of a logical partition (LPAR) established in a host, the method comprising:
establishing a logical path to an LPAR;
receiving a first notice from the LPAR that an IPL of the LPAR has commenced;
storing the address of the LPAR in a data structure indicating active IPL processing;
initiating a pack change state interrupt;
comparing the stored address with the addresses in a list of all LPARs to which the pack change state interrupt is directed;
if the list of addresses includes the stored address, removing the stored address from the list;
transmitting the pack change state interrupt to only the addresses in the list;
receiving a second notice from the LPAR that the IPL of the LPAR has completed; and
removing the address of the LPAR from the data structure.

2. The method of claim 1, further comprising, prior to transmitting the pack change state interrupt to the addresses in the list, placing only the addresses in the list in a queue.

3. The method of claim 1, wherein the first and second notices from the LPAR comprise a single command with an IPL indicator, the IPL indicator having first and second states.

4. The method of claim 3, wherein the single command comprises a defined subsystem operation command.

5. The method of claim 1, wherein the first notice from the LPAR comprises a first command and the second notice from the LPAR comprises a second command.

6. The method of claim 5, wherein the first and second commands each comprise a defined subsystem operation command.

7. A method for managing an initial program load (IPL) of a logical partition (LPAR) established in a host, the method comprising:
commencing an IPL of an LPAR, the LPAR having a worldwide network node number (WWNN) as an address;
establishing a logical path to a storage controller;
transmitting a first notice, including the WWNN, to the storage controller of the IPL that an IPL of the LPAR has commenced, whereby the storage controller stores the WWNN of the LPAR and whereby further the storage controller does not send a pack change interrupt to the LPAR address; and
transmitting a second notice, including the WWNN, to the storage controller of the completion of the IPL, whereby the storage controller deletes the WWNN of the LPAR from its storage.

8. The method of claim 7, wherein the first and second notices from the LPAR comprise a single command with an IPL indicator, the IPL indicator having first and second states.

9. The method of claim 7, wherein the first notice from the LPAR comprises a first command and the second notice from the LPAR comprises a second command.

10. A method for deploying computing infrastructure, comprising integrating computer readable code into a computing system, wherein the code, in combination with the computing system, is capable of performing the following:
establishing a logical path to a logical partition (LPAR);
receiving a first notice from the LPAR that an initial program load (IPL) of the LPAR has commenced;
storing the address of the LPAR in a data structure indicating active IPL processing;
initiating a pack change state interrupt;
comparing the stored address with the addresses in a list of all LPARS to which the pack change state interrupt is directed;
if the list of addresses includes the stored address, removing the stored address from the list;
transmitting the pack change state interrupt to only the addresses in the list;
receiving a second notice from the LPAR that the IPL of the LPAR has completed; and
removing the address of the LPAR from the data structure.

11. The method of claim 10, wherein storing the address in the data structure
comprises storing a worldwide network node number of the LPAR in the data structure.

12. The method of claim 10, wherein the first and second notices from the LPAR comprise a single command with an IPL indicator, the IPL indicator having first and second states.

13. The method of claim 12, wherein the single command comprises a defined subsystem operation command.

14. The method of claim 10, wherein the first notice from the LPAR comprises a first command and the second notice from the LPAR comprises a second command.

15. The method of claim 14, wherein the first and second commands each comprise a defined subsystem operation command.