APAR status
Closed as program error.
Error description
When WLM is decompressing data received it can get in a loop, the following stack can be seen in javacore: at java/util/Arrays.copyOf(Arrays.java:3580(Compiled Code)) at java/io/ByteArrayOutputStream.grow(ByteArrayOutputStream.java:12 9(Compiled Code)) at java/io/ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStre am.java:104(Compiled Code)) at java/io/ByteArrayOutputStream.write(ByteArrayOutputStream.java:1 64(Compiled Code)) (entered lock: java/io/ByteArrayOutputStream@0x000000002A454E50, entry count: 1) at com/ibm/ws/cluster/Compressor.decompress(Compressor.java:219(Com piled Code)) (entered lock: java/util/zip/Inflater@0x0000000019BA5000, entry count: 1)
Local fix
N/A
Problem summary
**************************************************************** * USERS AFFECTED: Users of IBM WebSphere Application Server * * Network Deployment using Linux on z15 * * hardware * * with hardware compression enabled * **************************************************************** * PROBLEM DESCRIPTION: An apparent hang occurs in the server, * * with high CPU consumption and steady * * memory growth * **************************************************************** * RECOMMENDATION: * **************************************************************** A defect (IJ26478) exists in Linux on zSeries Java levels prior to 8.0.6.16 wherein, when hardware compression is enabled on z15 systems, the compressed data is invalid in a way that can prevent decompression processes from detecting that the decompression has actually finished. In this specific case, the Work Load Manager component compresses cluster description data to send to other processes. When that data is decompressed, the failure to read the end of the compressed data results in an endless loop that also adds bytes to a data structure. In that case, the process will hang until eventually running out memory.
Problem conclusion
Mitigation was added to the Work Load Manager component to avoid the endless loop. Note that there are other potential issues caused by the faulty data compression, and for that reason IJ26478 should be applied even if this APAR is present. The fix for this APAR is targeted for inclusion in fix packs 8.5.5.19 and 9.0.5.7. For more information, see 'Recommended Updates for WebSphere Application Server': https://www.ibm.com/support/pages/node/715553
Temporary fix
Comments
APAR Information
APAR number
PH27505
Reported component name
WEBS APP SERV N
Reported component ID
5724H8800
Reported release
900
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2020-07-16
Closed date
2020-10-15
Last modified date
2020-10-15
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
WEBS APP SERV N
Fixed component ID
5724H8800
Applicable component levels
R850 PSY
UP
R900 PSY
UP
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Document Information
Modified date:
01 November 2021