Early next year, almost any information ever collected by Alexandria agencies on the city's 30,000 homes, businesses and public buildings will be available to city officials at the touch of a keyboard.

By then, the more than 15 million pieces of information now crammed into file cabinets throughout city government offices will have been fed into the $250,000 Geographic Based Management Information System as the first step toward making it the computerized know-it-all of city records.

That should put within the grasp of the computer system the kind of information that could help redraw police beats, indicate to firefighters where arson trouble spots exist and alert the public works department where new traffic signals should be installed.

"We are quite excited about it," said George Coyler, Alexandria's director of comprehensive planning. "This will be revolutionary for people like us." He said that for the first time city agencies will be able to "follow what the hell is going on in the city."

Once the information is in the computer base, city officials say they will be able to punch any address in Alexandria into the computer and get information about such things as who owns the property, if there is a building at that address and its type of structure, assessed value, floor space, use and complete background on the building's compliance with health, fire and building codes, as well as the number and type of fire and police calls made to the address.

The system will also be able to churn out maps, bar graphs and pie charts illustrating neighborhood trends discovered in its voluminous data bank of facts and figures.

Coyler's office is in the last stages of tediously preparing a map of Alexandria that is the key to the new computer system's ability to turn out graphics based on statistical information from areas as small as part of a city block.

City data-processing officials say that for decades various city departments have routinely gathered information for their own use but never had a reliable way to share that information with other agencies. Therefore, field workers from one agency were often sent out to collect information that was, at least in part, already in another agency's files.

The geography-based system, slated for completion in 1985, will change all that, said Robert J. Breimann, Alexandria's data-processing chief.

"This way everyone knows what everyone is doing," Breimann said, adding that all information in the computer will be filed by city street addresses and updated regularly.

"It will certainly be quite a benefit for the police," said Sgt. William Boyce, who helped tailor the system to police needs. "We feel service will improve as a result of it."

Using the new system, Boyce said, a police dispatcher will be able to verify a caller's address, determine any recent police runs for similar complaints in the area and what happened after police arrived.

"If we were answering a complaint of a loud party," Boyce said, "it would be good to know if there had been trouble in the past. If they beat up a police officer, that would help quite a bit in determining how to respond."

City officials say precautions will be taken to maintain the confidentiality of some files, such as criminal records of juveniles or lists of those treated for venereal disease at public clinics.

Councilman Donald C. Casey said he does not see the new city computer system as a threat to citizens' privacy because "it won't have anything that isn't already in city files."

But this computerized access to information will not be limited to city government, its officials say. Plans include a citizens' service and inquiry system that would provide information about pest control, street repair and cleaning, sewer repair and maintenance and weed cutting in the city's neighborhoods.

"I guess a lot of our talk sounds grandiose," said Theodore Summers, deputy director of data processing. "But we will be the only ones with something like this."

Jack Richards, a computer science director for Planning Research Corp. in McLean, said Alexandria's geography-based system will put it ahead of other area governments in meeting the mounting demands to gather and sort information.

"Everybody is talking about it," said Richards, "but Alexandria is there."