In GT.M's database engine, processes cooperate with one another to manage the database. To effect this cooperation, GT.M processes use UNIX Interprocess Communication (IPC) resources to coordinate and control access to the database and journal files, implement M LOCKs, and for database replication. This appendix helps you understand GT.M's IPC resource utilization.

This appendix includes two sections.

  • The first section contains an exercise to identify "orphan" shared memory segments (those with no attached processes) in a multi-site replication configuration. Usually orphan segments appear due to certain abnormal terminations (for example, kill -KILL or a process crash situation) and create an out-of-design state for GT.M IPC resources where the last process may not be able to clean up the shared memory segment. If you know the IPC resources GT.M uses, then you can easily find the abnormal IPC resources when something does not seem right.

  • The second section describes role of the gtmsecshr daemon process GT.M uses to manage M locks and clean up IPC resources. This section also includes guidelines to fine-tune gtmsecshr for smooth operation.

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