Caché High Availability Guide - InterSystems Documentation

1. Quiesce (pause) the database (this prevents any writes from occurring or locks from beingtaken out).2. Separate the disk mirror from production (if advanced disk technologies are used), ormake a copy of the Cache.dat files.3. Resume Caché.Backup Methods4. If a mirror was split off, backup the mirror copy of the database, and rejoin the mirror toproduction.2.3.1.3 Cold BackupThe cold backup strategy is generally used in the rare case when the operation toleratesdowntime. Often, smaller installations that do not have strict 24/7 access requirements usethis strategy. Sometimes, this is done only when performing a complete system backup aspart of a maintenance effort such as repairing faulty hardware. In this situation, stop Cachéduring the backup period and restart it when the backup completes.• Advantages — Very simple procedure (stop Caché and copy the cache.dat files).• Disadvantages — Caché must be stopped; so, of all the backup options, this methodinvolves the longest downtime.Procedure Outline:1. Stop Caché using the ccontrol command or through the Caché Cube.2. Perform the backup.3. Restart Caché using the ccontrol command or through the Caché Cube.2.3.2 Online BackupCaché implements a proprietary backup mechanism designed to cause very minimal or, inmost cases, no downtime to users of the production system. The online backup captures onlyblocks that are in-use by the database. The output goes to a sequential file (or directly to tape,though not recommended). The backup file is then copied to the backup media along withany other external files such as the .cpf file, the CSP files, and external files used by theapplication.The Caché backup uses a multipass scan to backup database blocks. It is expected that eachpass has a reduced list of modified blocks and that generally three passes are sufficient tocomplete a backup. During the entire final pass and for a brief moment during each priorCaché High Availability Guide 21